Thermal stability of Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.47/In/sub 0.53/As/InP heterostructure and its improvement by phosphidization

A drastic decrease in the sheet carrier concentration of the modulation-doped Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.47/In/sub 0.53/As/InP heterostructure has been observed after O/sub 2/ plasma treatment followed by thermal treatment up to 350/spl deg/C. It has been found that the decrease in sheet carrier concentration is caused by the impurities penetrated from the surface of the epilayer, and can be suppressed substantially by using PH/sub 3/ plasma treatment prior to the O/sub 2/ plasma and thermal treatments.