Highly transmittive semiconductor base for ballistic electron emission microscopy

In this work we introduce a molecular beam epitaxy (MBE)-grown InAs layer as base in ballistic electron emission spectroscopy/microscopy (BEES/BEEM). Compared to the commonly used thin metal film as base, the transmission coefficient and the attenuation length can be enhanced by more than one order of magnitude. At low temperatures (T = 100 K), a passivated InAs layer yields an attenuation length of the order of 70-90 nm, instead of the 5 nm obtained on Au films. This feature makes InAs a promising new base material for BEEM. To clarify the mechanism of this behaviour, temperature-dependent BEEM studies on InAs-GaAs heterostructures were performed. Unlike samples with metal base layers, it is found that the transmission coefficient of the InAs base decreases with decreasing temperature. In addition, a strong increasing conduction band offset at the InAs/GaAs interface with decreasing temperature is observed.