AlInN/GaN heterostructures with indium contents between 20% and 35% were grown by metal organic vapour phase epitaxy on high purity silicon (1 1 1) substrates. The samples were investigated by photovoltage (PV) spectroscopy whereby the individual layers were distinguished by their different absorption edges.

The near band-edge transitions of GaN and of Si demonstrate the existence of space charge regions within the GaN layers and the Si substrate. In sandwich geometry the Si substrate significantly influences the PV spectra which are strongly quenched by additional 690 nm laser light illumination. The intensity dependence and the saturation behaviour of quenching suggest a recharging of Si- and GaN-related interface defects causing a collapse of the corresponding PV signals in the space charge region.

From additional scanning surface potential microscopy measurements in bevel configuration further evidence of the existence of different space charge regions at the GaN/AlN/Si and AlInN/GaN interfaces is obtained.

The properties of the Si/seed layer/GaN heterostructure are discussed in terms of a p-type Si/n-type GaN layer interface generated by diffusion of Si atoms into GaN and of Ga or Al atoms into the Si substrate.

Source:IOPscience

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