Electrically-pumped WGM microlaser realized in n-AlGaN/n-ZnO:Ga microwire/Pt/MgO/p-GaN double heterojunction device

Abstract

The achievement of electrically-pumped laser diodes at the micro/nanoscale levels is anticipated to feature an indispensable role in future photonic integrated circuits. However, the conventional p-n junction device architectures are not efficient due to serious optical and electrical losses. Herein, an electrically-injected whispering-gallery mode (WGM) microlaser diode based on n-AlGaN/n-ZnO:Ga microwire/Pt/MgO/p-GaN double heterostructure was fabricated and systematically investigated. In practice, upon continuous-wave operation of electrical pumping at ambient temperature, the proposed device exhibits remarkable double heterojunction (n-n-p) characteristics, enabling it to lasing in the ultraviolet spectral region, accompanied by an efficient suppression of spontaneous radiation. Furthermore, the device exhibits fascinating properties with a threshold as low as 12.5 mA, and a high quality ($Q$)-factor of approximately 1943. The carefully-designed double heterojunction enables superinjection of current, companied with efficient confinement of injected carriers and photons. In this case, the electron-hole recombination, lasing region, and population inversion zones coincide, which are mainly concentrated in the ZnO:Ga MW active region, thereby achieving the required population inversion at relatively low current-injection levels. Such a methodical design and construction of a double heterojunction microlaser device could bring new technological opportunities to realize a high-performance lasers with low-threshold current, high $Q$-factor, distinct multiple-mode, and efficient suppression of spontaneous radiation driven by electrical excitation.