Investigation of p-contact performance for indium rich InGaN based light emitting diodes and solar cells.

We report on the optimization of p-GaN layers for high indium (In) content InGaN applications by optimizing temperature, precursor CP₂Mg flow rate and III/V ratio and report also on the optimization of p-contact performance. Using MOVPE, a 150 nm thick p-type GaN with moderate Mg doping and a 50 nm contact layer with high Mg doping concentration were grown on standard GaN templates at growth temperatures in the range of 850-1000 °C. Hall measurement yields hole concentration of 4.8 × 10¹⁷ cm⁻³ for the optimized sample. SIMS shows Mg concentration of 1.7 × 10²⁰ cm⁻³ on average in the heavily doped and 4 × 10¹⁹ cm⁻³ on average in the moderately doped p-GaN layer for the optimized p-GaN. A multilayer Pd/Ag/Ni/Au metal contact has been deposited on this p-GaN and studied using the CTLM technique. Optimization of both p-GaN layers and p-contact processing led to a low resistance contact with specific contact resistivity of 6 × 10⁻⁴ Ω cm². We believe, the very high Mg concentration of the surface layer in intimate contact with the contact metal reduces the Schottky barrier height and band bending. This optimization of p-GaN is an important step towards high efficiency green LEDs and solar cells. [ABSTRACT FROM AUTHOR]