Abstract
Abstract The effect of V-pits in the upper waveguide (UWG) on device performance of GaN-based laser diodes (LDs) has been studied. Experimental results demonstrate that in comparison with the LDs with u-In0.017Ga0.983N/u-GaN multiple UWG or u-In0.017Ga0.983N one, the LDs with a single u-GaN UWG has the best device performance. They have a smaller threshold current density, and a larger and more stable output optical power. The lowest threshold current density is as low as 1.3 kA/cm2, and the optical power reaches to 2.77 W. Furthermore, atomic force microscopy suggests that the deterioration of device performance of former kinds of devices may be attributed to the increase of V-pits’ size and quantity in the undoped-In0.017Ga0.983N UWG layer, and these V-pits could introduce more nonradiative recombination centers and exacerbate the inhomogeneity of injection current. Moreover, theoretical calculation results indicate that the increase of leakage current and optical loss are additional reasons for the device performance deterioration, which may be caused by a reduction of the potential barrier height for electrons in the quantum wells and by an increased background electron concentration in UWG.
Highlights
GaN-based laser diodes (LDs) have important application prospects in car headlights, general lighting, atomic clocks, portable projection, laser-based TVs, underwater communication, quantum technology and high-density optical data storage [1,2,3,4,5,6,7,8,9,10,11]
GaN-based blue-violet LDs would be related to the V-pits in the upper waveguide (UWG) layer, and an increase of leakage current and optical loss is another reason according to the theoretical calculation result by LASTIP
It is noted that except for LDI, the optical power of LDII and LDIII increases first and decreases abruptly when the current increases up to 3 A. It means that the device performance of LDI is the best among the three LDs, i.e. having the lowest threshold current, the largest peak optical power and the most stable output. This experimental result demonstrates that the device performance could be weakened when using the unintentionally doped-GaN layer (u-GaN)/u-In0.017Ga0.983N multiple UWG layer or using a u-In0.017Ga0.983N UWG layer
Summary
GaN-based laser diodes (LDs) have important application prospects in car headlights, general lighting, atomic clocks, portable projection, laser-based TVs, underwater communication, quantum technology and high-density optical data storage [1,2,3,4,5,6,7,8,9,10,11]. A great progress has been made in the last 30 years since Nakamura demonstrated the first GaN-based blue-violet diode lasers in 1990 [12, 13]. Less attention is put forward to build a connection between the V-pits in UWG layer and the device performance of GaN-based LD, extensive works have focused on the V-pits’ structural feature, formation mechanism [21,22,23] and influence on the performance of light-emitting diodes [24, 25] and solar cells [26, 27]. Liang et al.: Performance deterioration of GaN-based laser diode by V-pits in the upper waveguide layer. GaN-based blue-violet LDs would be related to the V-pits in the UWG layer, and an increase of leakage current and optical loss is another reason according to the theoretical calculation result by LASTIP
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