Heavy Si doping in AIGaAs near modulation-doped heterointerfaces

Abstract

We propose that the local Fermi-level modulation that occurs at heterojunctions enables the achievement of a higher carrier concentration in a limited thin layer than that can be achieved in a thick layer. We studied heterojunctions consisting of Si-doped AlGaAs (Al=20%) (AlGaAs:Si)/InGaAs (In=20%) grown by metalorganic chemical vapor deposition to demonstrate effectiveness of our doping method. The thickness and doping concentration of the AIGaAs:Si were designed carefully not to form a neutral region in the structure. We obtained a maximum electron concentration Nd=2.4×1019cm-3 at 300 K in AlGaAs:Si; this value is about seven times higher than that reported for AlGaAs:Si so far. We believe that the AlGaAs/InGaAs heterojunction positions the Fermi level in the AlGaAs:Si (near the heterojunction) far from the conduction-band minimum, and that this effectively suppresses creation of compensation centers in AlGaAs:Si, then all the Si donors in AlGaAs:Si are activated. © 1999 American Institute of Physics.