Extreme radiation resistance in InN

Carrier dynamics were studied in InN, which is a promising material for radiation-resistant optoelectronic devices. InN epilayers with different background electron densities were prepared by metal-organic chemical vapor deposition and irradiated with protons. Application of the light-induced transient grating technique in the sub-picosecond domain allowed to study the carrier lifetime and diffusion coefficient as a function of the total carrier density (intrinsic, photoexcited, and irradiation-induced). The dominance of the direct Auger process in carrier recombination was revealed. The irradiation of InN by protons, such as those encountered in space applications, decreases the carrier lifetime while simultaneously increasing the diffusion coefficient (up to 190 cm2/s at the highest total carrier density studied). As a result, the average carrier diffusion length does not decrease below ∼140 nm, and exceeds the light absorption depth of InN. The lifetime damage factor was determined, and the lifetime dependence on the displacement damage dose was measured. The radiation resistance of InN surpasses that of GaAs, InGaAs, and InGaN. InN-based photovoltaic devices may work for long space missions.