Deep level analysis in (AlGa)As-GaAs MODFETs by means of low frequency noise measurements

Low frequency noise of modulation doped field effect transistors manufactured from (AlGa) As-GaAs heterostructures was investigated. The layers for the test devices were grown by molecular beam epitaxy and contain a two-dimensional electron gas at the (AlGa) As-GaAs interface. Noise spectra were measured in a frequency range from 1 Hz to 25 kHz under different bias and temperature conditions. The results show a superposition of three generation-recombination noise components which are related to deep levels in the (AlGa) As layer with activation energies 0.40, 0.42 and 0.60 eV. These traps were also detected independently by deep level transient spectroscopy in similar (AlGa) As layers.