Drain current DLTS analysis of recoverable and permanent degradation effects in AlGaAs/GaAs and AlGaAs/InGaAs HEMT's

We present a detailed study of drain current DLTS spectra performed on asreceived and failed A1GaAs/GaAs and A1GaAs/InGaAs HEMT's of four different suppliers submitted to hot-electron tests. We demonstrate that a remarkable correlation exists between DLTS features and permanent and recoverable degradation effects. In particular, different behaviours have been found: (i) recoverable effects seems to be correlated with modulation of charge trapped on DX and ME6 centers. (ii) permanent degradation consisting in a decrease in Id and V T is due to negative charge trapping and is associated with a large increase of a peak having Ea=l.22 eV in the DLTS spectra of failed devices; (iii) development of traps in the gate-to-drain access region induces a permanent increase in drain parasitic resistance Rd and decrease in Id, and is correlated with the growth of a "hole-like" peak in DLTS spectra measured after hot-electron tests.