Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current-spreading layer

Abstract

This work reports both experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN (PNPNP-GaN) current spreading layers in p-GaN. Each thin n-GaN layer sandwiched in the PNPNP-GaN structure is completely depleted due to the built-in electric field in the PNPNP-GaN junctions, and the ionized donors in these n-GaN layers serve as the hole spreaders. As a result, the electrical performance of the proposed device is improved and the optical output power and EQE are enhanced. Tansu, "Design and characteristics of staggered InGaN quantum-well light-emitting diodes in the green spectral regime," IET Optoelectron. 3(6), 283-295 (2009

Self-screening of the quantum confined Stark effect by the polarization induced bulk charges in the quantum barriers

“…Other simulation parameters such as the Shockley-Read-Hall recombination lifetime of 43 ns, Auger recombination coefficient of 1 Â 10 À30 cm 6 /s, and the band offset ratio of 70/30 for the InGaN/GaN MQW can also be found in our previously published works. 13,[18][19][20][21][22] The electric field profiles under the equilibrium have been shown in Fig. 5(a).…”

On the origin of the electron blocking effect by an n-type AlGaN electron blocking layer

“…InGaN/GaN multiple quantum well (MQW) lightemitting diodes (LEDs) have made significant progress in the past three decades. [1][2][3] The device performance is, however, still limited by Auger recombination, 4,5 charge separation, 6-9 current crowding, [10][11][12] insufficient hole injection, 9,[13][14][15][16][17][18] and electron overflow from the MQW active region. [19][20][21][22] In order to address these issues, a staggered quantum well architecture and also InGaN/GaN MQWs with Si-step-doped quantum barriers have been proposed to screen the quantum confined Stark effect (QCSE) and increase the spatial overlap of electron-hole wave functions, [7][8][9] while an improved current spreading can be obtained either by making the p-type layer more resistive or the p-contact layer more conductive.…”

“…[19][20][21][22] In order to address these issues, a staggered quantum well architecture and also InGaN/GaN MQWs with Si-step-doped quantum barriers have been proposed to screen the quantum confined Stark effect (QCSE) and increase the spatial overlap of electron-hole wave functions, [7][8][9] while an improved current spreading can be obtained either by making the p-type layer more resistive or the p-contact layer more conductive. 10,11 Additionally, an improved crystal quality is also essential for improving the device efficiency. 23 Furthermore, it has been reported that an enhanced hole injection efficiency can be obtained through utilizing a thinner quantum barrier 17,18 or a thinner quantum well.…”

“…8 The simulation parameters regarding the Auger recombination coefficient, the Shockley-Read-Hall recombination lifetime and other nitrogen-contained simulation parameters can be found elsewhere, and specifically, considering the dislocation generation due to strain relaxation during the epitaxial growth, we have assumed a 40% polarization level. 8,10,11 The relationship among the captured electrons by quantum wells, mean free path and injected electrons can be expressed in Eqs. (1) and (2) …”

p-doping-free InGaN/GaN light-emitting diode driven by three-dimensional hole gas

“…1,2 To this end, tremendous efforts have been devoted to improve the LED performance through addressing various issues related to material quality, structure optimization, and device design and fabrication. [3][4][5][6][7][8][9][10][11][12] Among these issues, to date a low p-type doping efficiency remains as a limiting factor, which adversely affects the LED performance. In typical p-type GaN, the resulting hole concentration is low because only $1% of Mg dopants are ionized at room temperature.…”