Nanoporous GaN on p -type GaN: a Mg out-diffusion compensation layer for heavily Mg-doped p -type GaN.

Embedding p -type gallium nitride ( p -GaN) with controlled Mg out-diffusion in adjacent epitaxial layers is a key for designing various multi-junction structures with high precision and enabling more reliable bandgap engineering of III-nitride-based optoelectronics and electronics. Here, we report, for the first time, experimental evidence of how nanoporous GaN (NP GaN) can be introduced as a compensation layer for the Mg out-diffusion from p -GaN. NP GaN on p -GaN provides an ex-situ formed interface with oxygen and carbon impurities, compensating for Mg out-diffusion from p -GaN. To corroborate our findings, we used two-dimensional electron gas (2DEG) formed at the interface of AlGaN/GaN as the indicator to study the impact of the Mg out-diffusion from underlying layers. Electron concentration evaluated from the capacitance-voltage measurement shows that 9 × 10 12 cm -2 of carriers accumulate in the AlGaN/GaN 2DEG structure grown on NP GaN, which is the almost same number of carriers as that grown with no p -GaN. In contrast, 2DEG on p -GaN without NP GaN presents 9 × 10 9 cm -2 of the electron concentration, implying the 2DEG structure is depleted by Mg out-diffusion. The results address the efficacy of NP GaN and its' role in successfully embedding p -GaN in multi-junction structures for various state-of-the-art III-nitride-based devices.