Effect of channel doping on the low-frequency noise in GaN/AlGaN heterostructure field-effect transistors

We examined low-frequency noise in doped and undoped channel GaN/AlGaN/SiC heterostructure field-effect transistors with different Al content in the barrier. The observed noise spectra follow the 1/f(gamma) law with 0.8 less than or equal to gamma less than or equal to 1.2 for frequencies f up to 100 kHz. Our results indicate two orders of magnitude reduction in the input-referred noise spectral density in the undoped channel devices with respect to the noise density in the doped channel devices of comparable electric characteristics. Low temperature measurements reveal generation-recombination-type peaks in the spectra of the doped channel devices. Effects of the piezoelectric charges at the GaN/AlGaN interface are also discussed. (C) 1999 American Institute of Physics. [S0003- 6951(99)00740-8].