Far-infrared magnetoabsorption study of electron systems inGa0.47In0.53As-InP heterojunctions

Photoexcited and electric-field-excited far-infrared magnetoabsorption methods are applied for the first time to the degenerate and localized electron systems in ${\mathrm{Ga}}_{0.47}$ ${\mathrm{In}}_{0.53}$As-InP heterojunctions. The absorption under photoexcitation is sensitive to the fine structure of the system and gives effective masses of $m^{\mathrm{*}}$/$m_0$=0.047 and 0.043 for the two-dimensional electrons in the ground and the first excited subbands, respectively. The enhancement of the former from the bulk electron mass at the band edge is about 4 times larger than that of two-dimensional electrons in the GaAs-${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As heterojunction having the same sheet-electron concentration. This value is mainly attributed to the large band nonparabolicity in this system. In the electric-field-excitation experiments, the cyclotron-resonance peaks are found to move to higher fields due to the conduction-band nonparabolicity and the polaron coupling. From a detailed analysis of the phenomena the relative magnitudes of the shift turn out to be 5%, 9%, and 15% for bulk electrons and for two-dimensional electrons in the first-excited and ground subbands, respectively. If the result is considered with the quasi-Fermi-levels of these electron systems, the polaron-pinning effect is found to be essential in the hot-electronic cyclotron resonances. In addition, the Zeeman absorptions of the donor are clearly observed by the electric-field-excitation method and the donor binding energy in ${\mathrm{Ga}}_{0.47}$ ${\mathrm{In}}_{0.53}$As is confirmed as 3.0 meV.