An electrically-pumped WGM microlaser realized in an 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 inefficient due to serious optical and electrical losses. Herein, an electrically-injected whispering-gallery-mode (WGM) microlaser diode, which contained an n-AlGaN electron-injection layer, a ZnO microwire doped with a Ga impurity (ZnO:Ga MW), a Pt nanolayer, a MgO nanolayer and a p-GaN substrate as a hole supplier, was fabricated and systematically investigated. In practice, upon continuous-wave operation of electrical pumping at ambient temperature, the well-designed n-AlGaN/n-ZnO:Ga MW/Pt/MgO/p-GaN device exhibits remarkable double-heterojunction (n–n–p) characteristics, enabling lasing in the ultraviolet spectral region, accompanied by 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 heterostructure enables superinjection of current, as well as efficient confinement of injected carriers and photons. In this case, the electron–hole recombination, light-emission/lasing region, and population-inversion zones coincide, and 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 high-performance lasers with a low threshold, high Q-factor, distinct multiple modes, and efficient suppression of spontaneous radiation driven by electrical current.