High-power broad-area buried-mesa lasers

Abstract

Broad area lasers emitting near 940 nm are fabricated using a process based on two-step epitaxy. The n-side of the layer structure and the active layer are grown during the first epitaxial step, the p-side during the second. Between the first and the second step a shallow etching is used to remove the active layer from the two sides and at the two facets. This simple approach allows the creation of buried mesa lasers with non-absorbing mirrors, resulting in a reduced lateral current leakage, lower threshold current and higher efficiency, plus an increased robustness with respect to catastrophic optical damage.

High-brightness broad-area diode lasers with enhanced self-aligned lateral structure

“…It is also challenging to precisely control the implantation depth and damage profile due to the stochastic nature of implantation, with typical profiles spreading over hundreds of nanometres [20]. The BM structure in [12] has a built-in lateral refractive index guide, which allows the guiding of a larger number of higher-order lateral modes, and therefore leads to lower beam quality. The LBI structure in [13,14] is similar to the eSAS, but with a heavy-ion implantation step instead of the intermediate etching step.…”

“…However, the strong lateral index guiding in the RISAS would significantly increase BPP lat , making it unsuitable for realizing high-brightness BALs. The buried mesa structure (BM) is another confinement technique that has been implemented in BALs, in which the quantum well (QW) is etched outside of the central stripe between two growth stages [12]. In this structure, there is no true barrier to lateral current spreading, but carriers in the QW are still confined to the device center by lateral energy barriers that are created upon epitaxial regrowth, due to the higher band-gap energy of the regrown (waveguide) layers in comparison to the QW.…”

High power broad-area lasers with buried implantation for current confinement

“…We implanted Si in the p-side of the devices, to compensate the p doping and to create a reverse junction (in V1 structures) or to shift the position of the junction away from the QW (in V2 structures). Moving the junction away from the QW can have an insulation effect, increasing the turn-on voltage of the diode; a similar effect is described in [10].…”

“…In the case of variant V1 (figure 2, left), the second growth steps started with the growth of the GaAs sub-contact over the underlying GaAs etch-stop 2. In the case of variant V2 (figure 2, right) the etch-stop 2 was etched in situ, using CBr 4 , as described elsewhere [10], to remove it completely and to uncover the underlying AlGaAs inside the reactor, in order to minimize oxygen contamination. Subsequently, the growth started with AlGaAs.…”

“…More sophisticated approaches for the realization of lateral current confinement, introducing buried elements like a reverse junction or semi-insulating layers, involve wet chemical or dry etching and multi-step epitaxy processes on a patterned surface [8][9][10] with a resulting higher degree of technological complexity.…”