Neutron irradiation effects on electrical properties and deep-level spectra in undoped n-AlGaN∕GaN heterostructures

Abstract

The effect of neutron irradiation on the electrical properties of undoped n-AlGaN∕GaN heterostructures is reported. The two-dimensional electron-gas (2DEG) mobility starts to decrease at neutron doses above 1014cm−2, while the 2DEG concentration slightly increases at low doses and decreases dramatically for doses higher than 2.5×1016cm−2. The result is that the mobility/concentration product (a figure of merit for transistors) starts to decrease appreciably after the dose of 1015cm−2. Capacitance-voltage and admittance spectroscopies, indicate that tunneling of electrons into the states near Ec−0.21eV in AlGaN is a serious factor when cooling down the virgin or lightly irradiated samples. For heavily irradiated samples the states in AlGaN are close to 0.3 and 0.45eV, respectively, from the bottom of the conduction band. Deep-level spectroscopy measurements reveal the presence of hole traps with apparent activation energies of 0.18 and 0.21eV for lightly irradiated samples and deeper hole traps with activation energies of 0.6 and 1eV in heavily irradiated samples.