High-efficiency green micro-LEDs with GaN tunnel junctions grown hybrid by PA-MBE and MOCVD
Yaozheng Wu, Bin Liu, Feifan Xu, Yimeng Sang, Tao Tao, Zili Xie, Ke Wang, Xiangqian Xiu, Peng Chen, Dunjun Chen, Hai Lu, Rong Zhang, Youdou Zheng
Abstract
We fabricated p-i-n tunnel junction (TJ) contacts for hole injection on c -plane green micro-light-emitting diodes (micro-LEDs) by a hybrid growth approach using plasma-assisted molecular beam epitaxy (PA-MBE) and metal–organic chemical vapor deposition (MOCVD). The TJ was formed by an MBE-grown ultra-thin unintentionally doped InGaN polarization layer and an <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>++</mml:mo> </mml:mrow> </mml:msup> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">n</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msup> <mml:mtext>-</mml:mtext> <mml:mi>GaN</mml:mi> </mml:mrow> </mml:math> layer on the activated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msup> <mml:mi mathvariant="normal">p</mml:mi> <mml:mrow> <mml:mo>++</mml:mo> </mml:mrow> </mml:msup> <mml:mtext>-</mml:mtext> <mml:mi>GaN</mml:mi> </mml:mrow> </mml:math> layer prepared by MOCVD. This hybrid growth approach allowed for the realization of a steep doping interface and ultrathin depletion width for efficient inter-band tunneling. Compared to standard micro-LEDs, the TJ micro-LEDs showed a reduced device resistance, enhanced electroluminescence intensity, and a reduced efficiency droop. The size-independent J-V characteristics indicate that TJ could serve as an excellent current spreading layer. All these results demonstrated that hybrid TJ contacts contributed to the realization of high-performance micro-LEDs with long emission wavelengths.