Composition behaviour of energy band gaps in the alloy Al_xGa_yIn_1–x–ySb_zAs_1–z

Abstract

The principal energy band gaps [E($\mathrm{\Gamma }$), E(L), and E(X)] of the pentanary alloy $A{l}_{x}G{a}_{y}I{n}_{1-x-y}S{b}_{z}A{s}_{1-z}$ are calculated over the entire composition space (x,y, and z) using the universal tight-binding method based on $s{p}^3{s}^{\ast }$ basis functions. As the compositions x,y, and z increase, $E(\mathrm{\Gamma })$ increases rapidly and approaches E(X) or E(L). A direct-to-indirect transition occurs in the high-composition range of $x(x>\sim 0.8)$ because of either E(X) or E(L). It is found that the direct band-gap energy ranges from 0.18 to 1.98 eV. The independent composition effects of x, y, and z in the band gaps are investigated and compared with experimental data, and the results are in good agreement. In addition, the energy band gaps of the alloy $A{l}_{x}G{a}_{y}I{n}_{1-x-y}S{b}_{z}A{s}_{1-z}$ that were lattice matched on InAs and GaSb are found to be in the mid-infrared spectral range, which ranges from 0.35 to 0.57 eV (3.50–2.17 $\mathrm{\mu }$m) and 0.32 to 0.54 eV (3.88–2.29 $\mathrm{\mu }$m), respectively.

Keywords:

• energy band gap
• AlGaInAsSb
• mid-infrared (MIR)