Electron transport in unipolar InGaN/GaN multiple quantum well structures grown by NH3 molecular beam epitaxy

© 2015 AIP Publishing LLC. Unipolar-light emitting diode like structures were grown by NH3 molecular beam epitaxy on c plane (0001) GaN on sapphire templates. Studies were performed to experimentally examine the effect of random alloy fluctuations on electron transport through quantum well active regions. These unipolar structures served as a test vehicle to test our 2D model of the effect of compositional fluctuations on polarization-induced barriers. Variables that were systematically studied included varying quantum well number from 0 to 5, well thickness of 1.5 nm, 3 nm, and 4.5 nm, and well compositions of In0.14Ga0.86N and In0.19Ga0.81N. Diode-like current voltage behavior was clearly observed due to the polarization-induced conduction band barrier in the quantum well region. Increasing quantum well width and number were shown to have a significant impact on increasing the turn-on voltage of each device. Temperature dependent IV measurements clearly revealed the dominant effect of thermionic behavior for temperatures from room temperature and above. Atom probe tomography was used to directly analyze parameters of the alloy fluctuations in the quantum wells including amplitude and length scale of compositional variation. A drift diffusion Schrödinger Poisson method accounting for two dimensional indium fluctuations (both in the growth direction and within the wells) was used to correctly model the turn-on voltages of the devices as compared to traditional 1D simulation models.

Browne DA, Mazumder B, Wu Y-R, Speck JS (2015) Electron transport in unipolar InGaN/GaN multiple quantum well structures grown by NH3 molecular beam epitaxy. Journal of Applied Physics 117: 185703. Available: http://dx.doi.org/10.1063/1.4919750.

This work was supported by funding from the Solid State Lighting Program at UCSB and from the King Abdullah University of Science and Technology and the King Abdullah Center of Science and Technology. This work made use of the Central Facilities at UCSB supported by the NSF MRSEC program. A portion of this work was done in the UCSB Nanofabrication Facility, part of the NSF-funded National Nanotechnology Infrastructure Network. The work in NTU was support by Ministry of Science and Technology in Taiwan for the financial support, under Grant No. MOST-102-2221-E-002-194-MY3.

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