Design Considerations for GaN-Based Blue Laser Diodes With InGaN Upper Waveguide Layer

Abstract

Effects of an inserted InGaN interlayer between active region and p-AlGaN electron blocking layer on electrical and optical characteristics of GaN-based blue laser diodes are numerically investigated. It is found that the inserted InGaN interlayer reduces the barrier height for hole injection into multiple quantum wells. Moreover, it is found that the background electron concentration of the undoped InGaN plays a critical role in the LD performance. A background electron concentration higher than 1 × 10 17 cm −3 may induce undesired electron-hole recombination in this layer. In addition, we have calculated the dependences of optical confinement factor and internal absorption loss (IAL) on location, In composition, and thickness of the InGaN layer. A significant increase in OCF and a decrease in IAL are obtained by inserting the InGaN layer. Index Terms-Blue laser diodes (LDs), GaN, InGaN interlayer, internal absorption loss (IAL), optical confinement factor (OCF).

A comparative study of efficiency droop and internal electric field for InGaN blue lighting-emitting diodes on silicon and sapphire substrates

“…The Mg doping concentration of the p-GaN and p-AlGaN layers was 1 × 10 19 cm −3 , and the Si doping concentration of the n-GaN layer was 5 × 10 18 cm −3 . A background electron concentration of 1 × 10 17 cm −3 was assumed in the unintentionally doped QW and barrier layers 38 . The incomplete ionization of Mg acceptors and the field ionization model were included, and the AlGaN acceptor energy was linearly scaled from 170 meV in p-GaN to 470 meV in p-AlN 39 .…”

A Study of Efficiency Droop Phenomenon in GaN-Based Laser Diodes before Lasing

“…The laser structure under study is shown in Figure 1 , which is a conventional structure and has been reported in many studies [ 11 , 12 ]. It is composed of a 1000-nm-thick n -type GaN layer (Si: 3 × 10 18 cm −3 ), a 1000-nm-thick n -type Al 0.16 Ga 0.84 N/GaN superlattices (SLs) (Si: 3 × 10 18 cm −3 ), a 120-nm-thick n -type GaN lower waveguide layer (Si: 5 × 10 17 cm −3 ), the quantum-well (QWs) active region, a 20-nm-thick p -type Al 0.2 Ga 0.8 N electron blocking layer (EBL) (Mg: 4 × 10 19 cm −3 ), a 100-nm-thick p -type GaN upper waveguide layer (Mg: 1 × 10 19 cm −3 ), a 500-nm-thick p -type Al 0.16 Ga 0.84 N/GaN SLs (Mg: 2 × 10 19 cm −3 ), and a 40-nm-thick p -type GaN contact layer (Mg: 1 × 10 20 cm −3 ).…”

“…The characteristics of c -plane GaN-based LDs are simulated by using a commercial software LASTIP , from Crosslight Software Inc., Vancouver, BC, Canada. The simulator is based on finite element analysis of the drift-diffusion model with full Fermi–Dirac statistics for the transport equations as well as for the Poisson equation including the effect of polarization charges in two dimensions [ 11 ]. In the simulation, the activation energy of Mg acceptor is taken as 170 meV for GaN [ 13 ], which is assumed to increase 3 meV per 1% of Al increment for AlGaN alloy [ 14 ].…”

Improving the internal quantum efficiency of QD/QW hybrid structures by increasing the GaN barrier thickness

“…InGaN/GaN quantum wells (QWs) have been widely applied as the active region of light emitting diodes (LEDs) and laser diodes (LDs) in the blue, green and even yellow spectral regions. [1][2][3] However, the internal quantum efficiency (IQE) of InGaN/GaN QWs drop dramatically when the emission wavelength shis from the blue to green region. This problem is well known as the "green gap", [4][5][6] which is mainly caused by the high defect density and the quantum conned Stark effect (QCSE).…”