Free-carrier absorption and growth temperature of highly Be-doped InGaAs in molecular beam epitaxy

The current–voltage characteristics of p++-InGaAs/n-InP diodes grown by molecular beam epitaxy have been studied. When the substrates are directly radiatively heated during the growth (the so-called In-free mounting), a displacement of the electrical junction towards the n-type InP is observed for high doping ([Be]=9×1019cm-3). This effect comes from an increased Be diffusion, induced by an anomalous growth temperature increase. The growth temperature set point had to be decreased by 80 °C to recover the expected current–voltage characteristic. Optical absorption measurements carried out in single p++-InGaAs layer have shown the high strength of the inter-valence band absorption, which might be responsible for this significant temperature increase.