8.1 μ m-emitting InP-based quantum cascade laser grown on Si by metalorganic chemical vapor deposition

Abstract

This study presents the growth and characterization of an 8.1 μm-emitting, InGaAs/AlInAs/InP-based quantum cascade laser (QCL) formed on an InP-on-Si composite template by metalorganic chemical vapor deposition (MOCVD). First, for the composite-template formation, a GaAs buffer layer was grown by solid-source molecular-beam epitaxy on a commercial (001) GaP/Si substrate, thus forming a GaAs/GaP/Si template. Next, an InP metamorphic buffer layer (MBL) structure was grown atop the GaAs/GaP/Si template by MOCVD, followed by the MOCVD growth of the full QCL structure. The top-surface morphology of the GaAs/GaP/Si template before and after the InP MBL growth was assessed via atomic force microscopy, over a 100 μm2 area, and no antiphase domains were found. The average threading dislocation density (TDD) for the GaAs/GaP/Si template was found to be ∼1 × 109 cm−2, with a slightly lower defect density of ∼7.9 × 108 cm−2 after the InP MBL growth. The lasing performance of the QCL structure grown on Si was compared to that of its counterpart grown on InP native substrate and found to be quite similar. That is, the threshold-current density of the QCL on Si, for deep-etched ridge-guide devices with uncoated facets, is somewhat lower than that for its counterpart on native InP substrate, 1.50 vs 1.92 kA/cm2, while the maximum output power per facet is 1.64 vs 1.47 W. These results further demonstrate the resilience of QCLs to relatively high residual TDD values.

Quantum Cascade Lasers Grown by Metalorganic Chemical Vapor Deposition on Foreign Substrates with Large Surface Roughness

“…X-ray diffraction (XRD) analysis was used to examine the material's structural quality, as shown in Figure 4. The full width at half maximum (FWHM) of (004) InP peak for the QCL on Si and on GaAs 329 and 240 arcsec, respectively, are significantly larger compared to the value obtained from same laser structure grown on the on-axis Si (144 arcsec) with a low roughness InP buffer (1.5 nm) and moderately high TDD (7.9 × 10 9 cm −2 ) [5]. The rough buffer layer surface, together with a high density of dislocations, is a possible factor leading to the observed peak broadening.…”

“…The band structure for the lattice-matched QCL active region utilized in this study is based on a two-phonon resonance design [8]. This is also the same QCL structure previously adopted for realizing QCLs on on-axis GaAs and Si by MOCVD, and the growth details and full laser structure can be found here [4,5]. As shown in Figure 2, the QCL on the Si wafer was fabricated into a deep-etched ridge waveguide with an average core region width of ~25 µm.…”

“…Recently, a room-temperature continuous wave operation for MBE-grown QCLs on miscut Si substrates with an output power greater than 0.7 W and a low threshold current (1.3 kA/cm 2 ) has been achieved [3]. Meanwhile, our recent work shows that the InP-based QCLs on foreign substrates grown by metalorganic chemical vapor deposition (MOCVD) can also have a comparable device performance to its counterpart on native substrates, even in the presence of a high dislocation density [4][5][6]. However, these prior studies have not elucidated the role of the root-mean-square (RMS) surface roughness of buffer layers on subsequent device performances.…”

Recent progress in epitaxial growth of dislocation tolerant and dislocation free III–V lasers on silicon

“…Their unipolar carrier transport can bypass dislocation assisted electron-hole recombination (refer to figures 7(e) and (f)) [47,72]. Consequently, QCLs grown on Si can exhibit performance comparable to those grown on native III-V substrates [73,74]. In this scenario, rather than acting as nonradiative recombination centres, dislocations could affect the barrier/well interface quality, leading to poor electron tunnelling, reduced carrier lifetime, increased carrier leakage, and increased internal loss [72].…”

Development of high power, InP-based quantum cascade lasers on alternative epitaxial platforms

“…This laser was grown on a Ge/Si template using MBE. Another recent effort utilized a commercial GaP/Si template, on which a GaAs buffer was grown by MBE, followed by all MOCVD growth of an InP-based template and the QCL [17]. In this effort, the core was also lattice matched, targeting an emission wavelength of ~8.5 µm.…”