We have studied (AlxGa1-x)(0.5)In0.5P doped with tellurium using deep level
transient spectroscopy and associated electrical measurements. Several def
ect states are observed in the upper half of the band gap, that are believe
d to be intrinsic to the alloy system as well as related to the tellurium d
onors. Defects observed at measurement temperatures above 390 K exhibit a h
ysteretic behavior. The observed spectra depend on the biasing conditions a
pplied to the Schottky diode during cooling. The hysteretic behavior sugges
ts the existence of different defect configurations, which can be accessed
under conditions of high temperatures and electrical stress, but remain sta
ble below 300 K.