A novel InGaN-based bidirectional wavelength converter and optical amplifier based on hot electron-induced blue light-emitting device

In this work, the functioning of the Top-Hat Hot-Electron Light Emission and Lasing in a Semiconductor Heterostructure (TH-HELLISH) structure, which is based on InGaN/GaN multiple quantum wells, is investigated to employ it as an optical amplifier and wavelength converter. The heterojunction structure is formed by placing four InGaN quantum wells in the n-type GaN region between the n- and p-type GaN layers. The device with a TH-HELLISH structure was grown on a sapphire (Al2O3) substrate by Metal-Organic Chemical Vapor Deposition (MOCVD) with an indium ratio of 0.16. The TH-HELLISH device was fabricated in Top-Hat HELLISH (THH) geometry with four independent n- and p-channels contacts to create a non-isotropic potential distribution in the heterojunction. The electro-photoluminescence (E-PL) technique was used to obtain light amplification and the converted wavelength. A 370 nm excitation light is absorbed by the TH-HELLISH device, subsequently leading to the emission at 440±1 nm, which fulfills the role of a wavelength converter. It was also observed that TH-HELLISH operates as an optical amplifier with a 1.6-times increase in emission at 370 nm excitation. When the device is illuminated with a wavelength of 370 nm, it is monitored that the threshold electric field decreased from 0.25 kV/cm to 0.18 kV/cm, accompanied by a corresponding decrease in the threshold voltage from 12.5 V to 9.0 V. In addition, the TH-HELLISH device is found to be operated independently of the polarity of the applied voltage, and the absorption and emission regions of the device can be switched by changing the polarity of the applied voltage, therefore behaving as a bi-directional wavelength converter and optical amplifier.