UNIFORMITY STUDY IN PM-HEMT STRUCTURES AND DEVICES BY OPTICAL AND ELECTRICAL CHARACTERIZATION

We have studied the uniformity of both the structure and of the device characteristics of PM-HEMTs on (001) GaAs substrates. The structure u niformity was studied by photoreflectance modulation spectroscopy (PR) at room temperature and photoluminescence spectroscopy (PL) at low te mperature. PR was chosen for its main advantages of high sensitivity i n room temperature, higher than that of high temperature photoluminesc ence and non-destructiveness. We have studied the main transitions of the transistor structures using the 2DEG approximation. PR and PL resu lts yield uniformity with relative standard deviation (r.s.d.) lower t han 1%. After PR, transistors were fabricated on the wafers and tested for DC and RF characteristics and the results were correlated with th e PR data. The comparison between PR and PL has resulted in a strong i ndication that PR can be the technique of choice for the complete char acterization of structure uniformity of 3 inch pseudomorphic heterostr uctures, since it is non-destructive, relatively simple and can be per formed at room temperature. (C) 1998 Elsevier Science B.V. All rights reserved.