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Analysis of energy states of two‐dimensional electron gas taking into account the nonparabolicity of the conduction band
Author(s) -
Nishio Yui,
Tange Takahiro,
Hirayama Naomi,
Iida Tsutomu,
Takanashi Yoshifumi
Publication year - 2013
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201329259
Subject(s) - conduction band , electron , thermal conduction , fermi gas , energy (signal processing) , condensed matter physics , physics , quantum mechanics
We determined the energy states of a two‐dimensional electron gas (2DEG) in high electron mobility transistors (HEMTs) with a pseudomorphically strained InAs channel (InAs PHEMTs) rigorously, taking into account the nonparabolicity of the conduction band for InAs. To consider this nonparabolicity in the Schrödinger equation, we have used the energy‐dependent effective mass based on Kane's k · p perturbation theory. The Schrödinger equation was solved according to a standard perturbation theory by regarding the terms including the nonparabolicity parameter α ( ∼ 1 / E g ) as a perturbed Hamiltonian. Numerical simulation was carried out by solving the Schrödinger and Poisson equations self‐consistently. Since the effective mass of electrons increases with their energy, the Fermi energy E F and the first and second subband energies lie within the InAs well and hence most of the electrons are strongly confined in the InAs well. When the same calculation was done for conventional In 0.53 Ga 0.47 As HEMTs for comparison, there was no noticeable difference between the results for the parabolic and nonparabolic conduction‐band cases. In addition, it was found from the n s dependence of E F that the threshold voltage V TH for InAs PHEMTs is about 0.21 V lower than that for conventional In 0.53 Ga 0.47 As HEMTs. This V TH shift corresponds to the effective conduction‐band offset energy between the In 0.52 Al 0.48 As and InAs layers. The theoretical result for V TH agrees fairly well the experimental ones reported so far.