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9 Jul 1990

Volume 57, Issue 2, pp. 105-206

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Through‐thickness temperature gradients in double‐layered magneto‐optical media for direct overwrite

T. Ohtsuki, S. Owa, and F. Yamada

Appl. Phys. Lett. 57, 105 (1990); http://dx.doi.org/10.1063/1.103957 (3 pages) | Cited 2 times

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The effect of through‐thickness temperature gradients in thin films irradiated by short laser pulses is described, together with its application to direct overwrite. We found by simulation that through‐thickness temperature gradients become substantial when a medium is irradiated by short laser pulses of the order of 1 ns which is the characteristic time of heat diffusivity. This effect qualitatively explains why in writing experiments on a double‐layered medium short pulses expand the laser power range for a writing process.
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85.70.Sq Magnetooptical devices
42.79.Vb Optical storage systems, optical disks
44.30.+v Heat flow in porous media

Large increase of refractive index and compactness in siloxane‐type spin‐on‐glass induced by ion implantation

N. Moriya, Y. Shacham‐Diamand, and R. Kalish

Appl. Phys. Lett. 57, 108 (1990); http://dx.doi.org/10.1063/1.103958 (3 pages) | Cited 7 times

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Drastic changes in index of refraction and volume shrinkage of spin‐on‐glass films induced by P+ implantation are reported. An increase in refraction index (n) as large as 20% (from 1.38 to 1.79) has been measured following 1.6×1016 cm −2 implantations. The changes in n are accompanied by a volume shrinkage of similar magnitude. However, at doses exceeding ≊1015 cm−2 the shrinkage saturates while the index of refraction continues to increase indicating that material changes other than simple densification must be responsible for the observed rise in refractive index.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Jg Amorphous semiconductors; glasses
61.80.Jh Ion radiation effects
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Evaluation of LiB3O5 for second‐harmonic generation of femtosecond optical pulses

W. S. Pelouch, T. Ukachi, E. S. Wachman, and C. L. Tang

Appl. Phys. Lett. 57, 111 (1990); http://dx.doi.org/10.1063/1.104211 (3 pages) | Cited 8 times

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The optical characteristics of the new nonlinear crystal lithium triborate (LiB3O5) are evaluated for second‐harmonic generation (SHG) in the femtosecond regime. Using crystals grown in our laboratory, we demonstrate the use of LiB3O5 for autocorrelation measurements of ultrashort optical pulses. We find that pulse widths down to 40 fs can be measured accurately with crystal thicknesses varying from 0.195 to 4.165 mm. The effect of crystal length on the autocorrelation shape is also investigated.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.70.-a Optical materials

GaAs/AlGaAs multiple quantum well field‐induced optical waveguide

T. C. Huang, Y. Chung, N. Dagli, and L. A. Coldren

Appl. Phys. Lett. 57, 114 (1990); http://dx.doi.org/10.1063/1.103959 (3 pages) | Cited 9 times

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Electrically controllable optical waveguides have been created by using only the increase in refractive index from linear and quadratic electro‐optic effects in GaAs/AlGaAs multiple quantum well substrates for the first time. Unlike conventional fixed waveguides, lateral guiding of this field‐induced guide (FIG) can be turned on and off, so that the confinement factor, propagation constant, and net loss can be adjusted over wide ranges electrically. This special property plus a very simple fabrication process suggest that the FIG could be an important base technology for photonic integrated circuits.
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42.79.Gn Optical waveguides and couplers
78.20.Jq Electro-optical effects
85.60.-q Optoelectronic devices

Low‐threshold vertical cavity surface‐emitting lasers with metallic reflectors

E. F. Schubert, L. W. Tu, R. F. Kopf, G. J. Zydzik, and D. G. Deppe

Appl. Phys. Lett. 57, 117 (1990); http://dx.doi.org/10.1063/1.103960 (3 pages) | Cited 9 times

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Continuous‐wave room‐temperature operation is reported for the first time of vertical cavity current injection semiconductor lasers with a metallic reflector. The GaAs/(AlGa)As lasers have low‐threshold currents of 8 mA for 8‐μm‐diam contacts and threshold current densities of 9.5 kA/cm2. Single longitudinal mode and bimodal operation are obtained for short and long Fabry–Perot étalons, respectively. The spectral width of the single‐mode laser line is 0.1 Å. The laser structures have a very small series resistance which results in a voltage drop of 1.8 V along the diodes at lasing threshold.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Graded‐index optical fibers of methyl methacrylate‐vinyl benzoate copolymer with low loss and high bandwidth

Yasuji Ohtsuka, Eisuke Nihei, and Yasuhiro Koike

Appl. Phys. Lett. 57, 120 (1990); http://dx.doi.org/10.1063/1.103961 (3 pages) | Cited 10 times

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The interfacial‐gel copolymerization of 3/1, or 4/1 (wt/wt) methyl methacrylate‐vinyl benzoate monomer mixture followed by heat drawing results in graded‐index plastic optical fibers with attenuation loss of 212 and 134 dB/km at 652 nm, respectively, and with bandwidths of 170 and 260 MHz km, respectively, in comparison with 6 MHz km of the current step‐index plastic optical fiber. Now, it has been confirmed experimentally that graded‐index fibers are tremendously superior to step‐index fibers for data‐carrying capacity, while attenuation losses of both fibers are comparable.
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42.70.-a Optical materials
42.81.Ht Gradient-index (GRIN) fiber devices
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Excitonic effects in gain and index in GaAlAs quantum well lasers

Morris P. Kesler and Christoph Harder

Appl. Phys. Lett. 57, 123 (1990); http://dx.doi.org/10.1063/1.103962 (3 pages) | Cited 11 times

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Spontaneous emission and gain measurements in GaAlAs single quantum well lasers are presented. The gain is derived from the spontaneous emission detected through an opening in the top metallic contact of the lasers. Excitonic effects are seen in the gain (absorption) spectra for low carrier densities, and the step‐like nature of the two‐dimensional density of states is evident. From the gain spectra, refractive index changes are derived via a Kramers–Kronig transformation, and this is used to evaluate the linewidth enhancement factor as a function of photon energy.
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42.55.Px Semiconductor lasers; laser diodes
71.35.-y Excitons and related phenomena
78.45.+h Stimulated emission

Large third‐order optical nonlinearities in organic polymer superlattices

Samson A. Jenekhe, Wen‐Chang Chen, Saukwan Lo, and Steven R. Flom

Appl. Phys. Lett. 57, 126 (1990); http://dx.doi.org/10.1063/1.104116 (3 pages) | Cited 42 times

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Large second hyperpolarizabilities, 〈γxxxx〉, have been measured in solutions of two recently prepared organic polymer superlattices. These compounds have period aromatic and quinoidal structures and differ from each other by a side group substituent. The values observed are 1.6×10−29 esu for the parent copolymer and 3.7×10−30 esu for its acetoxy derivative. The corresponding values of χ(3)xxxx for the solid phase are estimated to be 2.7×10 −7 and 4.5×10−8 esu. Time‐resolved degenerate four‐wave mixing measurements, made at 532 nm, showed that the dynamics of the parent copolymer were faster than the 25 ps resolution of the instrument while the derivative exhibited an additional slower response component.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Bias‐lead monitoring of ultrafast nonlinearities in InGaAsP diode laser amplifiers

K. L. Hall, E. P. Ippen, and G. Eisenstein

Appl. Phys. Lett. 57, 129 (1990); http://dx.doi.org/10.1063/1.103963 (3 pages) | Cited 12 times

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In this letter we report the first femtosecond measurements of gain and loss dynamics in InGaAsP diode laser amplifiers using optically induced changes in diode junction voltage. Our results confirm that previously observed optical pump‐probe signals are related to carrier dynamics in the active region of the amplifiers.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Laser‐induced surface acoustic waves and photothermal surface gratings generated by crossing two pulsed laser beams

Akira Harata, Hiroyuki Nishimura, and Tsuguo Sawada

Appl. Phys. Lett. 57, 132 (1990); http://dx.doi.org/10.1063/1.103964 (3 pages) | Cited 61 times

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See Also: Erratum

Show Abstract
Gigahertz surface acoustic waves have been optically generated and detected on aluminum metallic films and silicon wafers using the laser‐induced grating technique. The acoustic velocities were in good agreement with those of Rayleigh waves. Photothermal surface gratings could also be detected as a nonpropagating component of the thermoelastic waves. The relaxation time of the grating was related to the thermal diffusivity of the material. A simplified theory for the generation of surface transient gratings containing acoustic waves is presented in addition to the experimental results.
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42.79.Dj Gratings
43.35.Pt Surface waves in solids and liquids
42.25.Fx Diffraction and scattering

Aligned and twinned orientations in epitaxial CoSi2 layers

H. Vanderstraeten, Y. Bruynseraede, M. F. Wu, A. Vantomme, G. Langouche, and J. M. Phillips

Appl. Phys. Lett. 57, 135 (1990); http://dx.doi.org/10.1063/1.104212 (3 pages) | Cited 15 times

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Heteroepitaxial CoSi2 layers have been made by ion beam synthesis and solid phase epitaxy in Si〈111〉 substrates. Using the x‐ray rocking curves of the asymmetric (331) reflections we are able to determine very accurately the relative amount of aligned (type A) and twinned (type B) CoSi2 in samples with different thicknesses. It is shown that for epilayers thinner than 360 Å, the relative amount of type A CoSi2 decreases from 100% to 30%.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Np Solid phase epitaxy; growth from solid phases

Dynamic observation of Si (111) surface using a fast scanning tunneling microscope

Sumio Hosaka, Tsuyoshi Hasegawa, Shigeyuki Hosoki, and Keiji Takata

Appl. Phys. Lett. 57, 138 (1990); http://dx.doi.org/10.1063/1.103965 (3 pages)

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Atomic structures of a Si (111) surface are dynamically observed at a 2 s/frame velocity over a scanning field about 150 Å×150 Å using a fast scanning tunneling microscope (FSTM). A FSTM has been developed and it features a compensation method for probe tip servo position error in the constant current mode. The compensation value is derived from the ratio of tunnel current fluctuation and tunnel current (Δ I/I) in differential‐type tunnel current equation. The FSTM provides first dynamic observation of a residual gas molecule adsorption on atomic defects in 7×7 Si adatom reconstructions using a video tape recorder. In addition, a thermal drift of about 10 Å /s, about 30 min after direct electric flash heating of the sample for Si surface cleaning, can be easily observed.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
68.35.Gy Mechanical properties; surface strains
68.35.B- Structure of clean surfaces (and surface reconstruction)

Photochemical hole burning of tetraphenylporphin in epoxy resin: Effect of crosslinked structure

Akira Furusawa, Kazuyuki Horie, Taro Suzuki, Shinjiro Machida, and Itaru Mita

Appl. Phys. Lett. 57, 141 (1990); http://dx.doi.org/10.1063/1.104117 (3 pages) | Cited 13 times

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Photochemical hole burning (PHB) of free‐base tetraphenylporphin (TPP) in epoxy resin was performed at 4.2–80 K. Effect of crosslinked structure of the epoxy resin on the dephasing time T2, low‐energy excitation modes, and the temperature dependence of Debye–Waller factor were studied through the PHB measurements. The excellent thermal stability of TPP in epoxy resin including the hole burning above liquid‐nitrogen temperature (80 K) was demonstrated.
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82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
81.40.Tv Optical and dielectric properties related to treatment conditions
42.70.-a Optical materials
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions

Relaxation of strained InGaAs during molecular beam epitaxy

G. J. Whaley and P. I. Cohen

Appl. Phys. Lett. 57, 144 (1990); http://dx.doi.org/10.1063/1.103966 (3 pages) | Cited 71 times

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Relaxation of strained InxGa1−xAs films grown on GaAs substrates has been measured in situ during molecular beam epitaxy growth by reflection high‐energy electron diffraction (RHEED). Growth is found to be layer by layer up to a strain‐dependent ‘‘critical’’ thickness where three‐dimensional clusters with {114} facets form. The onset of cluster growth is simultaneous with lattice relaxation as measured by RHEED. The relaxation during growth is compared with the Dodson–Tsao model for strained‐layer relaxation [Appl. Phys. Lett. 53, 1325 (1987)]. Two distinct mechanisms for relaxation were found depending on film strain. An activation energy for relaxation was measured to be 4.4 eV for a film strain of 2.3%. The relaxation deviated from the Dodson–Tsao model for nongrowth conditions.
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68.35.Gy Mechanical properties; surface strains
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.60.Bs Mechanical and acoustical properties
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Plasmons, photoluminescence, and band‐gap narrowing in very heavily doped n‐GaAs

Huade Yao and A. Compaan

Appl. Phys. Lett. 57, 147 (1990); http://dx.doi.org/10.1063/1.103967 (3 pages) | Cited 25 times

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The optical properties of extremely heavily doped n‐GaAs are examined. Metastable electron concentrations up to 3.2×1019 cm−3 were produced by pulsed‐laser annealing of Si‐implanted GaAs. These very heavily doped layers give plasmon Raman shifts up to 1700 cm−1 and photoluminescence bandwidths of greater than 410 meV. The low‐energy edge of the photoluminescence indicates a band‐edge narrowing proportional to ∼n1/3 and equal to ∼200 meV at the highest electron concentration.
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78.30.Fs III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
71.55.Eq III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Quantum‐switched heterojunction bistable bipolar transistor by chemical beam epitaxy

Ming C. Wu, Long Yang, and W. T. Tsang

Appl. Phys. Lett. 57, 150 (1990); http://dx.doi.org/10.1063/1.103968 (3 pages) | Cited 3 times

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We proposed and demonstrated a novel bistable transistor−the quantum‐switched heterojunction bistable bipolar transistor. The transistor has two current states. With increasing base‐emitter voltage, the collector current is switched from high to low, while the base current is switched from low to high. Bistability is observed for a certain range of base voltage. This device has potential applications in implementing high‐speed single bipolar transistor memories, gain quenching in light‐emitting devices, and optoelectronic switching.
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85.30.Pq Bipolar transistors
85.60.-q Optoelectronic devices
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)

New approach to projection‐electron lithography with demonstrated 0.1 μm linewidth

S. D. Berger and J. M. Gibson

Appl. Phys. Lett. 57, 153 (1990); http://dx.doi.org/10.1063/1.103969 (3 pages) | Cited 55 times

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We present a new approach to projection‐electron lithography which allows sub‐0.1 μm resolution to be achieved with short exposure times and a parallel illumination system. We have printed a grating pattern into PMMA with 0.1 μm linewidths. Our new technique consists of using an angularly limiting filter which differentiates electrons that have traversed a transparent mask in terms of the degree of scattering between the patterned and unpatterned regions.
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85.40.Hp Lithography, masks and pattern transfer
81.65.-b Surface treatments
06.60.-c Laboratory procedures
79.20.Kz Other electron-impact emission phenomena

Formation of low dislocation density silicon‐on‐insulator by a single implantation and annealing

M. K. EL‐Ghor, S. J. Pennycook, F. Namavar, and N. H. Karam

Appl. Phys. Lett. 57, 156 (1990); http://dx.doi.org/10.1063/1.104213 (3 pages) | Cited 10 times

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High quality silicon‐on‐insulator structures have been formed with dislocation densities in the top silicon layer below 104 cm−2 by oxygen implantation and one‐step annealing at 1300 °C for 6 h. Careful control of the implantation conditions is required in order to produce a high density of cavities in the top silicon layer. These cavities provide a stress‐free sink for silicon and oxygen interstitials, reducing the point‐defect supersaturations and, therefore, the nucleation and growth of oxide precipitates and dislocation loops. They also provide an internal surface which blocks free propagation of dislocation loops to the surface avoiding the formation of threading dislocations. With continued annealing, both the cavities and the oxide precipitates eventually dissolve, leaving a high quality silicon surface layer with a very low dislocation density.
Show PACS
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Temperature dependence of minority hole mobility in heavily doped silicon

Chih Hsin Wang, Konstantinos Misiakos, and Arnost Neugroschel

Appl. Phys. Lett. 57, 159 (1990); http://dx.doi.org/10.1063/1.103970 (3 pages) | Cited 13 times

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Temperature dependence of the minority hole mobility μp(ND,T) in heavily doped n+ silicon in the doping range from 1018 to 2.4×1019 cm−3 was investigated. The preliminary measurements show that the mobility is strongly temperature dependent. For temperatures below 200 K the minority‐carrier hole mobility increases with increasing doping, in contrast to the opposite dependence for the majority hole mobility in p+ silicon. Analytical fits to the measured data useful for low‐temperature modeling for bipolar devices are given.
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72.20.Dp General theory, scattering mechanisms
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Cw Elemental semiconductors

Chemical kinetics of hydrogen and (111) Si‐SiO2 interface defects

K. L. Brower and S. M. Myers

Appl. Phys. Lett. 57, 162 (1990); http://dx.doi.org/10.1063/1.103971 (3 pages) | Cited 68 times

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Electron paramagnetic resonance (EPR) measurements and theoretical considerations have yielded a unified model for the hydrogen chemistry of silicon dangling bond Pb defects at the (111)  Si‐SiO2 interface. Previous EPR measurements indicated that passivation of Pb centers with H2 proceeds by the reaction H2+Pb→HPb+H with an activation energy of 1.66±0.06 eV. New EPR studies reported here show that HPb centers dissociate by the reaction HPb→Pb+H with an activation energy of 2.56±0.06 eV. When combined, these two reactions yield H2→H+H, which in vacuum requires an energy input of 4.52 eV. Comparison of these energies indicates that the reverse reactions H+HPb→Pb+H2 and H+Pb→HPb occur with essentially no energy barrier and are controlled by the local availability of atomic hydrogen.
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68.35.Dv Composition, segregation; defects and impurities
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
76.30.Da Ions and impurities: general
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

Theoretical study of structures and growth of strained Si/Ge superlattices

Jian Zi, Kaiming Zhang, and Xide Xie

Appl. Phys. Lett. 57, 165 (1990); http://dx.doi.org/10.1063/1.103972 (3 pages) | Cited 14 times

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The geometry structures of strained (Si)n/(Ge)n (1≤n≤6) superlattices grown pseudomorphically on (001) oriented Si1−xGex (0≤x≤1) substrates are studied. The calculations indicate that with proper choice of the Ge composition factor x symmetrically strained superlattices can be approximately obtained, which might render the growth of a superlattice with larger thickness possible.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.B- Structure of clean surfaces (and surface reconstruction)

Growth velocity variations during metalorganic vapor phase epitaxy through an epitaxial shadow mask

P. Demeester, L. Buydens, and P. Van Daele

Appl. Phys. Lett. 57, 168 (1990); http://dx.doi.org/10.1063/1.103973 (3 pages) | Cited 11 times

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A novel shadow masking technique is proposed for the local variation of growth velocity in GaAs/AlGaAs structures grown on GaAs by metalorganic vapor phase epitaxy. This mask makes use of epitaxially grown spacer and mask layers and windows in the mask are lithographically defined. This results in a highly accurate and reproducible shadow mask which can be removed by lift‐off. Growth velocity variations up to 50% have been observed. The application of this technique to the coupling of passive and active waveguide structures is proposed.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
85.40.Hp Lithography, masks and pattern transfer

Chemical beam epitaxial growth of strained carbon‐doped GaAs

T. H. Chiu, J. E. Cunningham, J. A. Ditzenberger, and W. Y. Jan

Appl. Phys. Lett. 57, 171 (1990); http://dx.doi.org/10.1063/1.103974 (3 pages) | Cited 18 times

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We report an investigation of the growth characteristics of GaAs by chemical beam epitaxy using trimethyl‐Ga and arsine. The growth rate behaviors as a function of temperature, As overpressure, and alkyl arrival rate are qualitatively similar to those using triethyl‐Ga with differences that can be explained by differences in the alkyl‐Ga bond strength. A unified description of the growth kinetics assuming a unimolecular reaction mechanism is possible. Lattice parameter is found to decrease with increasing carbon concentration. A high quality GaAs/GaAs:C doping superlattice has been prepared. Although the composition modulation is too small for x‐ray diffraction measurement, the structural deformation gives rise to satellite peaks with order n up to ±7 observed for the first time. X‐ray analysis of the superlattice after annealing has been employed to study the carbon diffusion in GaAs.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
73.61.Ey III-V semiconductors
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Polar optic phonon and Γ→L intervalley scattering times in GaAs from steady‐state hot‐electron luminescence spectroscopy

W. Hackenberg and G. Fasol

Appl. Phys. Lett. 57, 174 (1990); http://dx.doi.org/10.1063/1.103975 (3 pages) | Cited 5 times

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We deduce the Γ→L intervalley and polar optic phonon scattering times of hot electrons in bulk GaAs from cw hot (e,A0) luminescence spectra at low excitation densities and their dependence on electron kinetic energy. We obtain the lifetime broadening due to these two processes from comparison with line shape calculations using a 16×16 k⋅p Hamiltonian, a full integration over k space, and a dipole model for the optical matrix elements. We find for the LO‐phonon emission time τLO=(132±10)fs. The threshold for Γ→L scattering is determined as 330±10 meV, above which a distinct decrease in total lifetime is observed. Γ→L scattering times of 150–200 fs are deduced, and we discuss a corresponding deformation potential.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Dp General theory, scattering mechanisms
78.55.Cr III-V semiconductors

Electron concentration and mobility loss in GaAs/GaAlAs heterostructures caused by reactive ion etching

W. Beinstingl, R. Christanell, J. Smoliner, C. Wirner, E. Gornik, G. Weimann, and W. Schlapp

Appl. Phys. Lett. 57, 177 (1990); http://dx.doi.org/10.1063/1.103976 (3 pages) | Cited 14 times

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We have investigated the influence of reactive ion etching on the properties of a two‐dimensional electron gas in GaAs/GaAlAs heterostructures at 4.2 K. After removing the GaAs cap layer and overetching on the surface of the n‐GaAlAs with CCl2F2 under various etching conditions we observe both a reduction of the electron concentration and a low‐field mobility loss which are correlated with ion energy. We ascribe this mobility loss to a capture of electrons into traps created by the etching process. Ion energies around 25 eV were found to meet best the requirements for low damaging as well as anisotropic etching, whereas energies exceeding 35 eV result in a complete depletion of the two‐dimensional electron gas.
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61.80.Jh Ion radiation effects
81.65.-b Surface treatments
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
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