Junction Temperature-Controlled Spectrum in a Two-Color InGaN–GaN Quantum-Well Light-Emitting Diode

We demonstrate the dependence of the output spectrum on the Ohmic-contact thickness in a blue/green two-color InGaN-GaN quantum-well (QW) light-emitting diode. By decreasing the metal thickness of the p-type Ohmic contact on the device, the contact resistance is increased and hence the junction temperature is raised. With the junction temperature raised, the probability for the hole to escape from the first QW (green emitting) and be captured by the next QWs is increased for more effective emission of blue light such that the blue/green intensity ratio can be adjusted. The conclusion of higher junction temperature in a sample of a thinner p-type metal layer is consistent with the measurement results of output power versus injection current and current versus applied voltage. The measurement based on the transmission-line method also shows the increasing trend of contact resistance in decreasing the p-type metal thickness