The pseudomorphic AlGaAs/InGaAs/GaAs MODFET, intended for future applications in cryoelectronics. has been investigated. In the temperature range of 10-350 K no collapse nor Kink effect have been detected. However, a threshold shift has been observed which is thought to be associated with electrically active defects in the heterostructure. The related deep levels are directly characterized by two electrical techniques: capacitance deep level transient spectroscopy and drain current transient spectroscopy. Experimental results establish the complementarity of both techniques.