Powering pacemakers from heartbeat vibrations using linear and nonlinear energy harvesters

M. Amin Karami and Daniel J. Inman

The authors design linear low frequency and nonlinear mono-stable and bi-stable energy harvesters to continuously recharge the batteries of the pacemakers by converting the vibrations from the heartbeats to electrical energy. They show that the proposed energy harvesters are robust to variation of heart rate and can meet the power requirement of pacemakers.

Appl. Phys. Lett. 100, 042901 (2012) | Read the press release

High-efficiency thin-film InGaP/InGaAs/Ge tandem solar cells enabled by controlled spalling technology

D. Shahrjerdi, S. W. Bedell, C. Ebert, C. Bayram, B. Hekmatshoar, K. Fogel, P. Lauro, M. Gaynes, T. Gokmen, J. A. Ott, and D. K. Sadana

The authors demonstrate the effectiveness of the controlled spalling technology for producing high-efficiency (28.7%) thin-film InGaP/(In)GaAs/Ge tandem solar cells. The authors used the technique to separate the as-grown solar cell structure from the host Ge wafer followed by its transfer to an arbitrary Si support substrate.

Appl. Phys. Lett. 100, 053901 (2012)

Effect of the graded electron blocking layer on the emission properties of GaN-based green light-emitting diodes

Ning Zhang, Zhe Liu, Tongbo Wei, Lian Zhang, Xuecheng Wei, Xiaodong Wang, Hongxi Lu, Jinmin Li, and Junxi Wang

The authors investigated the effect of a graded AlGaN electron blocking layer (GEBL) on the emission properties of InGaN/GaN multiple quantum wells light-emitting diode (LED). Their results indicate the adoption of GEBL in the LED enhances the electroluminescence intensity and reduces the wavelength blue-shift with increasing injection current.

Appl. Phys. Lett. 100, 053504 (2012)

Improved photoresponse of InAs/GaAs quantum dot infrared photodetectors by using GaAs_1−xSb_x strain reducing layer

Chia-Tze Huang, Yu-Cheng Chen, and Si-Chen Lee

The authors investigated the effect of a GaAs_1−xSb_x strain reducing layer on the performance of InAs/GaAs quantum-dot infrared photodetectors (QDIPs). The authors show that by increasing the Sb concentration to 20%, the resulting type-II structure provided a higher barrier for enhancing electron confinement, thus improving the spectral responsivity and operation temperature.

Appl. Phys. Lett. 100, 043512 (2012)

Effect of an electron blocking layer on the piezoelectric field in InGaN/GaN multiple quantum well light-emitting diodes

Dong-Yul Lee, Sang-Heon Han, Dong-Ju Lee, Jeong Wook Lee, Dong-Joon Kim, Young Sun Kim, and Sung-Tae Kim

The authors report the effect of an electron blocking layer (EBL) on the piezoelectric field in InGaN/GaN multiple quantum well light-emitting diodes (LEDs). LEDs with a p-AlGaN EBL exhibited reduced blueshift and a sublinear increase of full width at half maximum in their EL spectra at low current densities.

Appl. Phys. Lett. 100, 041119 (2012)

Giant electro-mechanical energy conversion in [011] cut ferroelectric single crystals

Wen D. Dong, Peter Finkel, Ahmed Amin, and Christopher S. Lynch

The authors demonstrate giant electro-mechanical energy conversion under a ferroelectric/ferroelectric phase transformation in [011] cut and poled lead titanate-based relaxor perovskite morphotropic single crystals. They found that under mechanical pre-stress, a relatively small oscillatory stress drives the material reversibly between rhombohedral and orthorhombic phases with a remarkably high polarization and strain jump induced at zero bias electric field and room temperature. The measured electrical output per cycle is more than an order of magnitude larger than that reported for linear piezoelectric materials.

Appl. Phys. Lett. 100, 042903 (2012)

Model of random telegraph noise in gate-induced drain leakage current of high-k gate dielectric metal-oxide-semiconductor field-effect transistors

Ju-Wan Lee and Jong-Ho Lee

The authors propose a model to explain the generation mechanism of appreciable random telegraph noise (RTN) in the gate-induced drain leakage (GIDL) current of the high-k gate dielectric MOSFETs and explain uncorrelated RTNs in the GIDL and the gate ET currents.

Appl. Phys. Lett. 100, 033501 (2012)

Advantages of blue InGaN light-emitting diodes with InGaN-AlGaN-InGaN barriers

Yen-Kuang Kuo, Tsun-Hsin Wang, and Jih-Yuan Chang

The authors demonstrate that the performance of the blue InGaN LEDs is markedly improved when the GaN barriers are replaced by InGaN-AlGaN-InGaN barriers due to the appropriately modified energy band diagrams, high carrier injection efficiency, uniform distribution of carriers in the QWs, high radiative recombination rate in the active region, and small efficiency droop.

Appl. Phys. Lett. 100, 031112 (2012)

Pulsed metal organic chemical vapor deposition of nearly latticed-matched InAlN/GaN/InAlN/GaN double-channel high electron mobility transistors

JunShuai Xue, JinCheng Zhang, YaoWei Hou, Hao Zhou, JinFeng Zhang, and Yue Hao

The authors report successfully growing high quality, nearly lattice-matched InAlN/GaN/InAlN/GaN double-channel heterostructures on sapphire by pulsed-metal-organic-chemical-vapor-deposition (PMOCVD). The authors were able to obtain high values of electron mobility and two-dimensional-electron-gas density.

Appl. Phys. Lett. 100, 013507 (2012)

Fundamental limits on optical transparency of transparent conducting oxides: Free-carrier absorption in SnO₂

H. Peelaers, E. Kioupakis, and C. G. Van de Walle

The authors use first-principles computational methods to study free-carrier absorption (FCA) in n-type SnO₂, a commonly used transparent conducting oxides (TCO) material. The authors found that tin dioxide only weakly absorbs visible light, thus letting most light pass through, so that it is still a useful transparent contact. The transparency of SnO₂ declined when moving to other wavelength regions.

Appl. Phys. Lett. 100, 011914 (2012) | Read the press release