Nitride-based LEDs with an SPS tunneling contact Layer and an ITO transparent contact

The indium-tin-oxide [ITO(80 nm)] and Ni(5 nm)-Au(10 nm) films were separately deposited on glass substrates, p-GaN layers, n⁺-InGaN-GaN short-period-superlattice (SPS) structures, and nitride-based light-emitting diodes (LEDs). It was found that ITO on n⁺-SPS structure could provide us an extremely high transparency (i.e., 93.2% at 465 nm) and also a reasonably small specific contact resistance of 1.6×10^-3Ω·cm². Although the forward voltage which corresponds to 20-mA operating current for LED with ITO on n⁺-SPS upper contact was slightly higher than that of the LED with Ni-Au on n⁺-SPS upper contact, a 30% higher output intensity could still be achieved by using ITO on n⁺-SPS upper contact. Moreover, the output power of packaged LED with ITO was about twice as large as that of the other conventional Ni-Au LEDs.