OMVPE-grown (Al xGa 1− x) 0.5In 0.5P/InGaAs MODFET structures: growth procedure and Hall properties

Abstract

Modulation doped (Al x Ga 1- x ) 0.5In 0.5P/In y Ga 1- y As/GaAs single quantum well structures have been grown by low pre ssure metal organic vapour phase epitaxy and characterized by Hall measurements and cathodoluminescence. The high conduction band offset in this structure is favourable for the fabrication of MODFET structures with high two-dimensional electron gas densities in the In y Ga 1- y As channel. Electron sheet densities up to 2.75 x 10 12 cm -2 have been obtained for x = 0.4 and y = 0.3 with appropriate doping. The structures have excellent Hall properties at room temperature and at 77 K. The critical interface between the InGaAs channel layer and the AlGaInP barrier layer has been improved by placing a thin AlGaAs interlayer (1.8 nm thick) between these two layers. This arrangement provides an abrupt interface between quantum well and interlayer and suppresses the interaction of the two-dimensional electron gas in the quantum well with the non-ideal interface between the interlayer and the AlGaInP barrier layer. Cathodoluminiscence studies revealed that the mechanism of strain relaxation in these structures is distinctly different from the mechanism observed in AlGaAs/InGaAs/GaAs heterostructures grown by molecular beam epitaxy. The results of this first study on AlGaInP/InGaAs/GaAs heterostructures lend strong support to the hypothesis that structures of this type are capable to displace AlGaAs/InGaAs/GaAs heterostructures for the fabrication of high speed field effect transistors on GaAs substrates.