Growth and annealing conditions of high Al-content p-type AlGaN for deep-UV LEDs

We report on growth and annealing conditions for high Al-content p-type AlGaN that is required to achieve deep-ultraviolet (UV) light-emitting diodes (LEDs) or laser diodes (LDs). Mg-doped AlGaN epilayers with the Al-contents between 0 and 40% were grown by low-pressure (LP) metalorganic chemical vapor deposition (MOCVD). We found that the suitable annealing temperature for p-Al0.22Ga0.78N is around 900 °C, which is approximately 50 °C higher than that for p-GaN. We also demonstrated that the use of a lower V/III ratio and a higher growth temperature are preferable for the growth of high Al-content p-AlGaN, in comparison with the case of p-GaN. By controlling the growth and annealing conditions, we have achieved hole concentrations as high as 2.0 × 1018 cm–3 for Mg-doped AlGaN with an Al-content of 32% as determined by Hall effect measurement. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)