Electron Localization in Group III-V Semiconductor Compound
Alloys
Christopher Pashartis1 and Oleg Rubel1
1 Department
of Materials Science and Engineering,
McMaster University, Hamilton, Ontario, Canada
We explore the band structures of new III-V material zinc blende alloys composed of
B, N, Ga, As, In, Sb, and Bi for 1.55 µm wavelength telecommunication lasers and their
corresponding electron localization at atomic sites from first principles. Engineering III-V
semiconductors by mixing modifies their electronic properties including band gaps (Fig. 1a)
and lattice constants that are typically a blend of the original compounds and elements.
Isoelectronic elements often result in undesirable effects. Electron localization in the vicinity of band edges affects the efficiency of carrier transport and recombination in lasers and
solar cells. A new method has been developed to determine the electron localization from
muffin tin radii (atomic sites) using the scheme of outlier detection with quartiles of electron
probabilities. The advantage of this method is the ability to distinguish a strongly localized
electron within the atomic muffin tin radius from a baseline of delocalized electrons. Comparing the results with the unfolded band structures Bloch character; the outlier method
is in general agreement. The industry standard of InGaAs for 1.55 µm is shown to have
the least amount of localized electronic states near the band edges (Fig. 1b). Alternatively,
we find that the electron localization is increased, noticeably with the addition of B and
Bi, which affects both radiative and non-radiative recombination rates. To accommodate
future Group III-V semiconductor band engineering, we suggest design criteria to facilitate
the prediction of localization in new alloys.
1
2.5
DOS
0.180
OS
10
0.9
2.0
0.5
0.0
0.5
0.4
1
eV· nm 3
0.6
DOS
1.0
7
5
0.090
0.3
0.045
-0.5
0.2
-1.0
0.1
L
G
X
0
Localized DOS
0.135
0.7
Spectral weight
Energy (eV)
1.5
1
eV· nm 3
0.8
2
0
1.0
0.5
0.0
0.5
Wave vector
Energy (eV)
a)
b)
1.0
1.5
0.000
2.0
FIG. 1: Lattice matched In34 Ga30 As64 band structure from band unfolding (a) and the electron
localization scheme applied (b). In this case, the localization is significantly lower than the number
of states available at a given energy by two orders of magnitude.