Continuous-wave operation of m-plane GaN-based vertical-cavity surface-emitting lasers with a tunnel junction intracavity contact

Abstract

We have achieved continuous-wave (CW) operation of an optically polarized m-plane GaN-based vertical-cavity surface-emitting laser (VCSEL) with an ion implanted current aperture, a tunnel junction intracavity contact, and a dual dielectric distributed Bragg reflector design. The reported VCSEL has 2 quantum wells, with a 14 nm quantum well width, 1 nm barriers, a 5 nm electron-blocking layer, and a 23λ total cavity thickness. The thermal performance was improved by increasing the cavity length and using Au-In solid-liquid interdiffusion bonding, which led to lasing under CW operation for over 20 min. Lasing wavelengths under pulsed operation were observed at 406 nm, 412 nm, and 419 nm. Only the latter two modes appeared under CW operation due to the redshifted gain at higher temperatures. The peak output powers for a 6 μm aperture VCSEL under CW and pulsed operation were 140 μW and 700 μW, respectively. The fundamental transverse mode was observed without the presence of filamentary lasing. The thermal impedance was estimated to be ∼1400 °C/W for a 6 μm aperture 23λ VCSEL.

Nonpolar GaN-based VCSELs with lattice-matched nanoporous distributed Bragg reflector mirrors

“…Plots reprinted with permission. 64 Overlaid are the thermal resistance of reported CW-RT VCSEL by NCTU [88], Meijo-Stanley [71], and UCSB [89]. 115 xviii Tables Table 1.1 List of some dielectric materials used in DBRs [106].…”

“…This allows metal contact pads to be located away from the aperture (preventing light blocking) and the carriers are transported into the MQWs through an underlying spreading layer. For the p-side, the intracavity contact is usually a transparent conductive oxide such as indium-tin oxide (ITO) [74,88] or a nitridebased tunnel junction (TJ) [81,89], whereas for the n-side they are the highly doped bulk…”

GaN-based vertical-cavity surface-emitting lasers with tunnel junction contacts grown by metal-organic chemical vapor deposition

“…[4][5][6][7][8][9] Reports of III-nitride VCSELs have consisted of hybrid epitaxial=dielectric 10,11) and dual dielectric DBR designs. [7][8][9][12][13][14] Both designs have required intracavity contacts, and indium tin oxide (ITO) has been the most commonly used material to improve lateral current spreading on the p-side. However, the high absorption loss of ITO can lead to significantly higher threshold currents and lower light outputs.…”

“…In this device, we believe that the poor current-spreading layer and the variation of contact resistance in the TJ were the main causes, which were also shown in the I-V curve. Furthermore, surface residues after PEC etching, such as gallium oxide, 12) could also be another issue. Improvements in the TJ contact and current-spreading layers will likely lead to improved lateral mode profiles and lower operation voltage.…”

A Study of the Photoelectrochemical Etching of n-GaN in H3PO4 and KOH Electrolytes

“…It is thus an important complementary technology to plasma etching for use in certain applications. 8,10,[23][24][25][26] The most common method of wet etching for n-type Group-III nitrides is photoelectrochemical (PEC) etching. 19,20,22,[27][28][29][30][31][32][33][34][35][36][37][38][39][40] There have been several fundamental investigations of this process 35,36,40 using techniques such as linear sweep voltammetry, rotating disk voltammetry, electrochemical impedance and Mott-Schottky analysis.…”