Determination of AlGaN/GaN HEMT Reliability Using Optical Pumping as a Characterization Method

By pumping AlGaN/GaN HEMTs with below band-gap light we observe changes in drain current that correspond to the trapping and detrapping of carriers within the band-gap. These changes in drain current are indicators of trap density, since the energy from a specific wavelength of light pumps traps whose activation energies are less than or equal to that of the light source. AlGaN/GaN HEMTs on SiC with dual submicron gates with widths of 125nm, 140nm, or 170nm, are DC-stressed under three different conditions along a load line: V GS =0, V DS =5 (on-state), V GS =-2, V DS =9.2 and, V GS =-6, V DS =25 (off-state). The stress tests are interrupted at 20% degradation and the optically pumped comparisons to the baseline are measured. This paper describes the optical pumping technique and results from experiments of AlGaN/GaN HEMTs under the three DC stress biases along a load line.