Low-operation voltage of InGaN/GaN light-emitting diodes with Si-doped In0.3Ga0.7N/GaN short-period superlattice tunneling contact layer

InGaN/GaN multiple-quantum-well light-emitting diode (LED) structures including a Si-doped In0.23Ga0.77N/GaN short-period superlattice (SPS) tunneling contact layer were grown by metalorganic vapor phase epitaxy. The In0.23Ga0.77N/GaN(n(+))-GaN(p) tunneling junction, which the low-resistivity n(+)-In0.3Ga0.7N/GaN SPS instead of high-resistivity p-type GaN as a top contact layer, allows the reverse-biased tunnel junction to form a "ohmic" contact. In this structure, the sheet electron concentration of Si-doped In0.23Ga0.77N/GaN SPS is around I x 10(14)/cm(2), leading to an averaged electron concentration of around 1 x 10(20)/cm(3). This high-conductivity SPS would lead to a low-resistivity ohmic contact (Au/Ni/SPS) of LED. Experimental results indicate that the LEDs can achieve a lower operation voltage of around 2.95 V, i.e., smaller than conventional devices which have an operation voltage of about 3.8 V.