MOBILITY ENHANCEMENT IN MBE-GROWN INXGA1-XAS IN0.52AL0.48AS MODULATION-DOPED HETEROSTRUCTURES/

Pseudomorphic InxGa1-xAs/In0.52Al0.48As modulation-doped heterostructu res were grown by molecular beam epitaxy (MBE) on InP (100) substrates over a range of indium compositions from x=0.53 to 0.75. Low temperat ure photoluminescence (PL) measurements show a prominent reduction in the InGaAs linewidth due to the quantum-size effect as the indium comp osition is increased from its lattice-matched value of 0.53. The lowes t linewidth of 6.8 meV was achieved at an indium composition of 0.65, above which an increase in the linewidth was observed due to the overw helming effects of interfacial strain. The Hall mobilities at 300 K an d 77 K increase in correspondence to the PL linewidth reduction as the indium composition is increased. Although initial signs of mobility s aturation can be seen at an indium composition of 0.65, the peak mobil ity at 77 K of 8.9 x 10(4) cm(2) V s(-1) was achieved at an indium com position of 0.70. There is experimental evidence to indicate that the mobility enhancement at increasing indium composition is due to an eff ect of a reduction in the alloy scattering and in the effective mass o f the carriers. It was found that the insertion of an additional In0.5 3Ga0.47As interface smoothing layer between the strained InGaAs channe l and the In0.52Al0.48As spacer layer did not have a significant effec t on the mobility enhancement in the heterostructures. (C) 1996 Academ ic Press Limited