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22 Oct 2001

Volume 79, Issue 17, pp. 2681-2850

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Si3N4/AlGaN/GaN–metal–insulator–semiconductor heterostructure field–effect transistors

X. Hu, A. Koudymov, G. Simin, J. Yang, M. Asif Khan, A. Tarakji, M. S. Shur, and R. Gaska

Appl. Phys. Lett. 79, 2832 (2001); http://dx.doi.org/10.1063/1.1412591 (3 pages) | Cited 115 times

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We report on a metal–insulator–semiconductor heterostructure field-effect transistor (MISHFET) using Si3N4 film simultaneously for channel passivation and as a gate insulator. This design results in increased radio-frequency (rf) powers by reduction of the current collapse and it reduces the gate leakage currents by four orders of magnitude. A MISHFET room temperature gate current of about 90 pA/mm increases to only 1000 pA/mm at ambient temperature as high as 300 °C. Pulsed measurements show that unlike metal–oxide–semiconductor HFETs and regular HFETs, in a Si3N4 MISHFET, the gate voltage amplitude required for current collapse is much higher than the threshold voltage. Therefore, it exhibits significantly reduced rf current collapse. © 2001 American Institute of Physics.
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85.30.Tv Field effect devices
81.65.Rv Passivation

Effect of average grain size on the work function of diamond films

Patrick Abbott, Edward D. Sosa, and David E. Golden

Appl. Phys. Lett. 79, 2835 (2001); http://dx.doi.org/10.1063/1.1412825 (3 pages) | Cited 9 times

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The work function of hydrogen-terminated polycrystalline diamond films deposited by electrophoresis on molybdenum was studied using ultraviolet photoelectron spectroscopy with 21.2 eV photons for average grain sizes ranging from 0.32 to 108 μm. The work function has a maximum of about 5.1 eV at 0.32 μm, then decreases with increasing grain size to a minimum of about 3.2 eV at an average grain size of about 4 μm and then increases to a value of about 4.8 eV at a grain size of 108 μm. The results are consistent with a model in which the work function is controlled by the work function of single crystal diamond (111) at the larger grain sizes, graphitic carbon at the smaller grain sizes, and by a negative electron affinity that increases with decreasing grain size due to defects near diamond (111) crystallite edges for the intervening grain sizes. The large change in work function (almost a factor of 2) could be useful to make conductors with different work functions for microelectronic gate structures. © 2001 American Institute of Physics.
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73.30.+y Surface double layers, Schottky barriers, and work functions
79.60.Bm Clean metal, semiconductor, and insulator surfaces
68.55.-a Thin film structure and morphology

High-speed visible-blind GaN-based indium–tin–oxide Schottky photodiodes

Necmi Biyikli, Tolga Kartaloglu, Orhan Aytur, Ibrahim Kimukin, and Ekmel Ozbay

Appl. Phys. Lett. 79, 2838 (2001); http://dx.doi.org/10.1063/1.1412592 (3 pages) | Cited 28 times

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We have fabricated GaN-based high-speed ultraviolet Schottky photodiodes using indium–tin–oxide (ITO) Schottky contacts. Before device fabrication, the optical transparency of thin ITO films in the visible-blind spectrum was characterized via transmission and reflection measurements. The devices were fabricated on n−/n+ GaN epitaxial layers using a microwave compatible fabrication process. Our ITO Schottky photodiode samples exhibited a maximum quantum efficiency of 47% around 325 nm. Time-based pulse-response measurements were done at 359 nm. The fabricated devices exhibited a rise time of 13 ps and a pulse width of 60 ps. © 2001 American Institute of Physics.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Hi Surface barrier, boundary, and point contact devices
85.30.Kk Junction diodes

N-side illuminated microcrystalline silicon solar cells

A. Gross, O. Vetterl, A. Lambertz, F. Finger, H. Wagner, and A. Dasgupta

Appl. Phys. Lett. 79, 2841 (2001); http://dx.doi.org/10.1063/1.1395518 (3 pages) | Cited 8 times

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Thin-film microcrystalline silicon solar cells illuminated through the n layer were studied and compared with classical p-layer illuminated cells. To investigate the corresponding charge carrier extraction properties, variation of the intrinsic absorber layer thickness was carried out. It was found that the J–V characteristic and the quantum efficiency of the n- and p-side illuminated cells are almost identical in the thickness range investigated, up to 7 μm. No differences in the collection of photogenerated electrons or holes are observed. Hence, the illumination side of μc-Si:H single junction solar cells of conventional thickness may be randomly chosen without adverse effect on their performance. © 2001 American Institute of Physics.
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84.60.Jt Photoelectric conversion
72.40.+w Photoconduction and photovoltaic effects
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