Modeling and design of an electrically pumped SiGeSn microring laser

Abstract

We present a suspended SiGeSn microring laser design that enables strain relaxation of the material layer stack, electrical pumping and adequate heat sinking. Using both strain and composition as two degrees of freedom to engineer the band structure, a direct bandgap is obtained in the gain material of a double heterostructure layer stack, and the L-to G-valley energy difference increased to 78 meV, by 66% compared to a non-underetched structure. The temperature dependent current threshold is modeled for the designed device and determined to be 18 kA/cm ! at 50 K. The fabrication process is outlined and first experimental electroluminescence results indicating the effectiveness of our approach are reported. At the time this proceedings paper is being submitted, electrically pumped lasing has also been achieved with a similar structure, with results that will be reported in a future publication.

Strain Engineered Electrically Pumped SiGeSn Microring Lasers on Si

“…28 Figure 2e shows the net modal gain versus injection-current density, at 50 K, for devices with R o = 5.5 μm, following previously made modeling assumptions. 22,28 Both a disk without inner hole and a ring with R i = 1 μm, that correspond to devices A and D (see Table 1), are modeled. For the ring's inner hole, the actual undercut length obtained from the crosssectional TEM has been considered.…”

“…The latter is composed of 60 nm doped to 2 × 10 18 cm –3 , followed by 20 nm 5 × 10 19 cm –3 , and facilitates the injection and transport of electrons into the active region with a reasonable series resistance. For holes, the device relies on defectivity driven p-doping of the lower layers . Prior to undercut, the as-grown optically active material features −0.35% biaxial compressive heteroepitaxial strain determined by X-ray diffraction.…”

“…For holes, the device relies on defectivity driven p-doping of the lower layers. 22 Prior to undercut, the asgrown optically active material features −0.35% biaxial compressive heteroepitaxial strain determined by X-ray diffraction. Figure 1a shows a transmission electron micrograph (TEM) of the heterostructure together with its elemental distribution obtained by secondary ion mass spectrometry (SIMS).…”

“…Electrically pumped lasing is measured up to 90 K with a threshold current-density as low as 25 kA/cm 2 at 5 K for the larger, 9 μm outer radius rings, consistent with simulations. 22…”

“…In addition to facilitating bidirectional strain relaxation, it improves routing of carriers to the optically active region and reduces the volume that needs to be pumped. Electrically pumped lasing is measured up to 90 K with a threshold current-density as low as 25 kA/cm 2 at 5 K for the larger, 9 μm outer radius rings, consistent with simulations …”