Room temperature photoluminescence evaluation of In0.29Al0.71As/In0.3Ga0.7As/GaAs metamorphic high electron mobility transistor structures

The optical and electrical properties of In0.29Al0.71As/In0.3Ga0.7As/GaAs metamorphic high electron mobility transistor (MM-HEMT) structures grown by molecular beam epitaxy were investigated. The RT PL spectrum shows four peaks, corresponding to In0.29Al0.71As layer grown at 380 °C (peak C), In0.29Al0.71As layer grown at 520 °C (peak D), the e2–hhl and e1–hhl transitions (the second electron and the first subband to first hole subband) in the channel, respectively. The deviation between peak C and peak D is attributed to In desorption due to high growth temperature, strain resulted from incomplete relaxation of metamorphic InAlAs. The sheet carrier concentration (Ns) and electron mobility (μ) decrease with the deviation increasing, which indicates the electrical properties depend on the quality of metamorphic MM buffers significantly. Therefore, the electrical properties of MM-HEMT can be nondestructively evaluated by room temperature PL spectra.