An InGaN-based horizontal cavity surface emitting laser diode

Tetsuya Akasaka, Toshio Nishida, Naoki Kobayashi, and Toshiki Makimoto
Materials Science Laboratory

@Group III-nitrides, such as AlN, GaN, InN, and their alloys, are attractive for application to optoelectronic devices in the visible and UV ranges, because these semiconductors have wide and direct bandgaps. The mirror facets of group III-nitride-based lasers have been fabricated by either cleaving or dry-etching. Selectively grown microfacets are better choices for fabricating mirror facets. In this work, we fabricated an InGaN-based horizontal cavity surface emitting laser diode (HCSELD) [1]. It is a Fabry-Perot laser diode that has a pair of cavity mirrors consisting of selectively grown vertical {11-20} microfacets and a pair of outer micromirrors consisting of the selectively grown inclined {11-22} microfacets. The outer micromirrors direct the laser beam upward. Successful room-temperature lasing of the InGaN-based HCSELDs has been achieved by current injection.
@Figure 1 shows an SEM birdfs-eye-view photograph of an InGaN-based HCSELD. It can be seen that a Fabry-Perot cavity mirror and an outer micromirror are a vertical {11-20} microfacet and an inclined {11-22} microfacet of the regrown Mg-doped GaN layers, respectively. The {11-20} Fabry-Perot cavity mirror of the HCSELD is vertical to a SiC substrate. The angle between the inclined {11-22} outer micromirror and the SiC substrate surface is 58 degrees. Therefore, geometrically, laser beams are emitted at an angle of 64 degrees to the substrate surface. The InGaN-based HCSELDs lase at room temperature (RT) by current injection. Spectra obtained below and above the lasing threshold are shown in Fig. 2. The narrowing of the spectrum can be seen at current density above the lasing threshold. The lasing wavelength is approximately 400 nm. We also observed the nonlinear change in the current-light output relationship at the lasing threshold. This is the first current-injection lasing of the nitride-based surface emitting laser diode.
[1] T. Akasaka et al., Appl. Phys. Lett. 84 (2004) 4104-4106.

Fig. 1.
Birdfs-eye-view SEM photograph of an InGaN-based HCSELD.
Fig. 2.
Emission spectra obtained from an InGaN-based HCSELD below and above the lasing threshold.