Original Publication Date
Journal of Applied Physics
DOI of Original Publication
Date of Submission
The band structure, quantum confinement of charge carriers, and their localization affect the optoelectronic properties of compound semiconductor heterostructures and multiple quantum wells (MQWs). We present here the results of a systematic first-principles based density functional theory (DFT) investigation of the dependence of the valence band offsets and band bending in polar and non-polar strain-free and in-plane strained heteroepitaxial In x Ga1- xN(InGaN)/GaN multilayers on the In composition and misfit strain. The results indicate that for non-polar m-plane configurations with [12¯10]InGaN // [12¯10]GaN and InGaN // GaN epitaxial alignments, the valence band offset changes linearly from 0 to 0.57 eV as the In composition is varied from 0 (GaN) to 1 (InN). These offsets are relatively insensitive to the misfit strain between InGaN and GaN. On the other hand, for polar c-plane strain-free heterostructures with [101¯0]InGaN // [101¯0]GaN and [12¯10]InGaN // [12¯10]GaN epitaxial alignments, the valence band offset increases nonlinearly from 0 eV (GaN) to 0.90 eV (InN). This is significantly reduced beyond x ≥ 0.5 by the effect of the equi-biaxial misfit strain. Thus, our results affirm that a combination of mechanical boundary conditions, epitaxial orientation, and variation in In concentration can be used as design parameters to rapidly tailor the band offsets in InGaN/GaN MQWs. Typically, calculations of the built-in electric field in complex semiconductor structures often must rely upon sequential optimization via repeated ab initio simulations. Here, we develop a formalism that augments such first-principles computations by including an electrostatic analysis (ESA) using Maxwell and Poisson's relations, thereby converting laborious DFT calculations into finite difference equations that can be rapidly solved. We use these tools to determine the bound sheet charges and built-in electric fields in polar epitaxial InGaN/GaN MQWs on c-plane GaN substrates for In compositions x = 0.125, 0.25,…, and 0.875. The results of the continuum level ESA are in excellent agreement with those from the atomistic level DFT computations, and are, therefore, extendable to such InGaN/GaN MQWs with an arbitrary In composition.
Dong, L., Mantese, J. V., & Avrutin, V., et al. Strain induced variations in band offsets and built-in electric fields in InGaN/GaN multiple quantum wells. Journal of Applied Physics, 114, 043715 (2013). Copyright © 2013 AIP Publishing LLC.
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VCU Electrical and Computer Engineering Publications