Study on avalanche breakdown and Poole-Frenkel emission in Al-rich AlGaN grown on single crystal AlN

We demonstrate that theoretical breakdown fields can be realized in practically dislocation free Al-rich AlGaN p-n junctions grown on AlN single crystal substrates. Furthermore, we also demonstrate a leakage current density in AlGaN that is independent of the device area, indicating a bulk leakage phenomenon and not surface or mesa-edge related. Accordingly, we identified the Poole-Frenkel emission from two types of point-defect traps in AlGaN as the primary source of reverse leakage before breakdown. Mg-doped AlGaN exhibited leakage currents due to a shallow trap at & SIM;0.16 eV in contrast with leakage currents observed in Si-doped AlGaN due to a deep trap at & SIM;1.8 eV.