Interface quality and electron transfer at the GaInP on GaAs heterojunction

Hall measurements performed on Ga0.50In0.50P/In0.20Ga0.80As structures show abnormally low mobility both at room temperature and at 77 K, and too high electron densities which cannot be attributed to a normal two-dimensional electron gas in the channel. On the other hand, low temperature photoluminescence on asymmetrical AlGaAs/GaAs/GaInP quantum wells and x-ray photoemission spectroscopy measurements reveal the presence of arsenic atoms in the GaInP barrier. Using a one-dimensional Schrödinger–Poisson simulation with a nonabrupt interface model, we show that the presence of arsenic in GaInP leads to the formation of a parasitic GaInAsP well between the δ-doped layer and the channel, trapping the main part of transferred electrons. We experimentally show that the electron transfer can be drastically improved by inserting a thin AlInP layer at the interface. Insertion of at least six monolayers of AlInP is needed to recover a normal electron transfer as high as 2.1×1012 cm−2.