TEMPERATURE-DEPENDENCE OF THE BAND-GAP ENERGY OF DISORDERED GALNP

The temperature variation of the photoluminescence peak energy of GaxIn1-xP shows a complex dependence on the structural order; however, such effects are not well explained even for the fully disordered material. The band-gap energy of disordered GaxIn1-xP was measured at temperatures from 10 to 300 K and the measured values were used to find the best parameters in a theoretical equation. Since a simpler expression does not fit the experimental data accurately (especially below 30 K), an expression consisting of three terms which represent the effect of thermal expansion, electron-optical-phonon coupling, and electron-acoustic-phonon coupling was adopted. Dividing an electron-phonon coupling term into two terms results in a better expression for InP over the entire range of measuring temperatures. This function was applied to disordered GaxIn1-xP (x = 0.5, 0.7). It is found that in InP the electron-acoustic-phonon coupling is stronger than electronoptical-phonon coupling, while in GaxIn1-xP the opposite is true.