Rapid thermal annealing effects on step-graded InAlAs buffer layer and $In0.52Al0.48As/In0.53Ga0.47As$ metamorphic high electron mobility transistor structures on GaAs substrates

A step-graded InAlAs buffer layer and an $In0.52Al0.48As/In0.53Ga0.47As$ metamorphic high electron mobility transistor (MM-HEMT) structures were grown by molecular beam epitaxy on GaAs (001) substrates, and rapid thermal annealing was performed on them in the temperature range $500–800 °C$ for 30 s. The as-grown and annealed samples were investigated with Hall measurements, and 77 K photoluminescence. After rapid thermal annealing, the resistivities of step-graded InAlAs buffer layer structures became high. This can avoid leaky characteristics and parasitic capacitance for MM-HEMT devices. The highest sheet carrier density $ns$ and mobility μ for MM-HEMT structures were achieved by annealing at 600 and $650°C,$ respectively. The relative intensities of the transitions between the second electron subband to the first heavy-hole subband and the first electron subband to the first heavy-hole subband in the MM-HEMT InGaAs well layer were compared under different annealing temperatures.