Compression of the dc drain current by electron trapping in AlGaN/GaN modulation doped field-effect transistors

The frequently observed dc drain current compression of AlGaN/GaN modulatio n doped field-effect transistors is associated with partial loss of the two -dimensional electron gas caused by electron trapping. The behavior of the temperature-dependent electron concentration and persistent photoconductivi ty at low temperature in the AlGaN/GaN modulation doped heterostructure are indicative of the presence of DX centers in the AlGaN layer. Deep-level tr ansient spectroscopy of the drain current reveals carrier trapping with act ivation energy of 0.28 eV. However, this value appears to be too small to e xplain the compression of the dc drain current or to attribute these traps to DX centers in AlGaN. (C) 2001 American Institute of Physics.