THE EFFECT OF ARSENIC SPECIES ON THE MINORITY CARRIER PROPERTIES OF (AlGa)As-GaAs DOUBLE HETEROSTRUCTURES GROWN BY MBE

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Abstract
The influence of arsenic molecular species, As2 or As4, on the minority carrier properties of beryllium doped, p-isotype (AlGa) As-GaAs double heterostructures has been studied. All the samples were grown at 650°C in an oil diffusion pumped system with extensive liquid nitrogen cryopanelling and vacuum interlock. The same batch of arsenic was used to prepare both the As2 and AS4 films. The choice of active layer thickness (1 µm) and doping level (NA-ND = 5x10l6 cm-3) ensured the sensitivity of the minority carrier lifetime to the properties of the (AlGa) As-GaAs interfaces. Measurements of the minority carrier lifetime in the GaAs performed using a photoluminescence decay technique showed the advantage of using As2 for the ternary cladding regions. Supplementary measurements of the external photoluminescence efficiency, under low excitation conditions, allowed us to estimate the interface recombination velocity at the (AlGa) As-GaAs interface and to place a minimum value (>6%) on the internal photoluminescence efficiency of the GaAs. We conclude that for alloys grown with As2 the interface recombination velocity is at least a decade lower than equivalent films grown with AS4

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