Abstract
Ultra-wide band-gap nitrides have huge potential in micro- and optoelectronics due to their tunable wide band-gap, high breakdown field and energy density, excellent chemical and thermal stability. However, their application has been severely hindered by the low p-doping efficiency, which is ascribed to the ultrahigh acceptor activation energy originated from the low valance band maximum. Here, a valance band modulation mode is proposed and a quantum engineering doping method is conducted to achieve high-efficient p-type ultra-wide band-gap nitrides, in which GaN quantum-dots are buried in nitride matrix to produce a new band edge and thus to tune the dopant activation energy. By non-equilibrium doping techniques, quantum engineering doped AlGaN:Mg with Al content of 60% is successfully fabricated. The Mg activation energy has been reduced to about 21 meV, and the hole concentration reaches higher than 1018 cm−3 at room temperature. Also, similar activation energies are obtained in AlGaN with other Al contents such as 50% and 70%, indicating the universality of the quantum engineering doping method. Moreover, deep-ultraviolet light-emission diodes are fabricated and the improved performance further demonstrates the validity and merit of the method. With the quantum material growth techniques developing, this method would be prevalently available and tremendously stimulate the promotion of ultra-wide band-gap semiconductor-based devices.
Highlights
Ultra-wide band-gap (UWBG) nitrides, as a new generation of semiconductor, have been playing a central role in the fields of efficient deep-ultraviolet illumination and detection, high-frequency and high-power electronic devices, due to their tunable direct UWBG, high breakdown field, excellent chemical and thermal stability1–3
We have theoretically proposed a VB modulation mode to achieve high-efficient p-type UWBG nitrides and have technically conducted a quantum engineering to realize the idea, in which GaN quantum-dots (QDs) are buried in UWBG nitride matrix to produce a new band edge (BE) in the system and to tune the system Ea
Projected density of states (PDOS) of the system and different N atoms are picked out to investigate the valance band maximum (VBM) shift because the N2p orbits mainly contribute to the VBM states (Fig. 2a)
Summary
Ultra-wide band-gap (UWBG) nitrides, as a new generation of semiconductor, have been playing a central role in the fields of efficient deep-ultraviolet illumination and detection, high-frequency and high-power electronic devices, due to their tunable direct UWBG, high breakdown field, excellent chemical and thermal stability. For UWBG nitrides, some issues including dopant solubility, self-compensation, and high acceptor activation energy (Ea), seriously hinder their efficient p-doping, gradually becoming the main obstacle in realizing highperformance devices. The solubility of the most frequently used Mg dopant, which is the major p-type dopant in nitrides, decreases sharply as the Al content increases. The formation energy (EF) of nitrogen vacancy (VN) is low and the VN density sharply increases as Al content promotes, which naturally provides excess electrons to compensate holes, further resulting in low ptype conduction. Issues of solubility and selfcompensation can be moderated by growth conditions
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