InGaN Laser Diodes with Etched Facets for Photonic Integrated Circuit Applications

Abstract

The main objective of this work is to demonstrate and validate the feasibility of fabricating (Al, In) GaN laser diodes with etched facets. The facets are fabricated using a two-step dry and wet etching process: inductively coupled plasma—reactive ion etching in chlorine, followed by wet etching in tetramethylammonium hydroxide (TMAH). For the dry etching stage, an optimized procedure was used. For the wet etching step, the TMAH temperature was set to a constant value of 80 °C, and the only variable parameter was time. The time was divided into individual steps, each of 20 min. To validate the results, electro-optical parameters were measured after each step and compared with a cleaved reference, as well as with scanning electron microscope imaging of the front surface. It was determined that the optimal wet etching time was 40 min. For this time, the laser tested achieved a fully comparable threshold current (within 10%) with the cleaved reference. The described technology is an important step for the future manufacturing of photonic integrated circuits with laser diodes integrated on a chip and for ultra-short-cavity lasers.

Monolithic 45 Degree Deflecting Mirror as a Key Element for Realization of 2D Arrays of Laser Diodes Based on AlInGaN Semiconductors

“…Figure 7 c shows the SEM images of the dry- and wet-etched facets of an individual proposed device fully possessed. It can be seen from the pictures that vertical laser facets are of very good quality [ 38 ].…”

Continuous‐Wave Operation of 457 nm InGaN Laser Diodes with Etched Facet Mirrors for On‐Chip Photonics

“…This can be done by evanescent coupling realized through wafer bonding, by transfer printing or by end-fire coupling using an etched facet laser, which is the topic addressed here. [8][9][10][11][12][13][14] GaN-based etched facet lasers use inductively coupled plasma (ICP) etching, which results in nonvertical facets and a large surface roughness and potential etch damage induced by highenergy ions leading to increased laser thresholds and mirror losses. To address these issues, crystallographic selective wet chemical etching of the exposed semiand nonpolar planes, most often with tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH), has been used to smoothen the facets, facilitated by the inert c-plane.…”

“…To address these issues, crystallographic selective wet chemical etching of the exposed semiand nonpolar planes, most often with tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH), has been used to smoothen the facets, facilitated by the inert c-plane. [14][15][16][17] In this work, we explain the mechanism by which the wet etching proceeds such that an optimized defect-free facet can be formed in the multilayer AlInGaN laser structure. We then apply the process and monitor the reduction in lasing threshold with etch time and characterize the resulting lasers.…”