Low-operation voltage of InGaN-GaN light-emitting diodes with Si-doped In/sub 0.3/Ga/sub 0.7/N/GaN short-period superlattice tunneling contact layer

InGaN/GaN multiple-quantum-well light-emitting diode (LED) structures including a Si-doped In/sub 0.23/Ga/sub 0.77/N/GaN short-period superlattice (SPS) tunneling contact were grown by metalorganic vapor phase epitaxy. In/sub 0.23/Ga/sub 0.77/N/GaN(n/sup +/)-GaN(p) tunneling junction, the low-resistivity n/sup +/-In/sub 0.3/Ga/sub 0.77/N/GaN SPS instead of high-resistivity p-type GaN as a top contact layer, allows the reverse-biased tunnel junction to form an "ohmic" contact. In this structure, the sheet electron concentration of Si-doped In/sub 0.23/Ga/sub 0.77/N/GaN SPS is around 1/spl times/10/sup 14//cm/sup 2/, leading to an averaged electron concentration of around 1/spl times/10/sup 20//cm/sup 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.