Frequency dependence of junction capacitance of GaN p–i–n UV detectors

Abstract

In this paper frequency dependence of small-signal capacitance of p–i–n UV detectors, which were fabricated on GaN grown on sapphire substrate by metalorganic chemical vapor deposition, has been studied. The Schibli–Milnes model was used to analyze the capacitance–frequency characteristics. According to high frequency C– V measurements, the deep level mean concentration is about 2.98 × 10 20 cm −3. The deep level is caused by the un-ionised Mg dopant. The calculated Mg activation energy is 260 meV and the hole thermal capture cross section of the deep level is about 2.73 × 10 −22 cm 2. The applicability of the Schibli–Milnes model is also discussed when the concentration of deep levels exceeds that of the heavily doped n-side. It is concluded that the analytic expression of the Schibli–Milnes model can still be used to describe the capacitance–frequency characteristics of GaN p–i–n UV detectors in good agreement with experiment.