Influence of Ⅴ/Ⅲ ratio on the structural and photoluminescence properties of In_(0.52) AlAs/In_(0.53) GaAs metamorphic high electron mobility transistor grown by molecular beam epitaxy

A series of metamorphic high electron mobility transistors (MMHEMTs) with different Ⅴ/Ⅲ flux ratios are grown on GaAs (001) substrates by molecular beam epitaxy (MBE).The samples are analysed by using atomic force microscopy (AFM),Hall measurement,and low temperature photoluminescence (PL).The optimum Ⅴ/Ⅲ ratio in a range from 15 to 60 for the growth of MMHEMTs is found to be around 40.At this ratio,the root mean square (RMS) roughness of the material is only 2.02 nm;a room-temperature mobility and a sheet electron density are obtained to be 10610.0cm 2 /(V · s) and 3.26 × 10 12 cm 2 respectively.These results are equivalent to those obtained for the same structure grown on InP substrate.There are two peaks in the PL spectrum of the structure,corresponding to two sub-energy levels of the In 0.53 Ga 0.47 As quantum well.It is found that the photoluminescence intensities of the two peaks vary with the Ⅴ/Ⅲ ratio,for which the reasons are discussed.