type-II Interband Cascade Lasers Research Articles

Midinfrared type-II interband cascade lasers

We describe the progress made in the development of type-II interband cascade lasers emitting in the midinfrared (3.8–3.9 μm) spectral region. Three nominally similar molecular beam epitaxy growths on substrates from different vendors show qualitatively different electrical and optical properties. The devices tested show significant improvements over previously reported results with respect to differential external quantum efficiency (∼500%), peak power (>4 W/facet), peak power conversion efficiency (∼7%), maximum operating temperature (217 K), and continuous-wave operation.

Interband cascade lasers: progress and challenges

Interband cascade (IC) lasers take advantage of the broken-gap alignment in type-II InAs/Ga(In)Sb heterostructures to reuse electrons for sequential photon emissions from successively connected active regions; thus, they represent a new class of mid-IR light sources. In this work, we describe recent progress in IC lasers at emission wavelengths of 3.8–3.9 μm; these lasers have exhibited significantly higher differential quantum efficiencies and peak powers than previously reported. These InAs/GaInSb type-II IC lasers were able to operate at temperatures up to 217 K, which is higher than the previous record (182 K) for an IC laser at this wavelength. We observed from several devices at temperatures above 80 K a slope greater than 750 mW/A per facet, corresponding to a differential external quantum efficiency exceeding 460%. A peak optical output power exceeding 4 W/facet and peak power efficiency of ∼7% were observed from a device at 80 K. Also discussed are challenging issues related to the reduction of threshold currents and power dissipation to further advance this new class of lasers.

Recent Progress of Mid-IR Type-II Interband Cascade Lasers

AbstractWe report the recent progress in type-II interband cascade (IC) lasers, For the 4.2-pm devices, lasing was observed up to 210 K, and the threshold density was only 95 A/cm2at 90 K and 284 A/cm2at 200 K. For the 4.5-μm lasers, the internal loss was only 11.6 cm−1 and the internal quantum efficiency was 460% at 90 K. We have also demonstrated the first dual-wavelength type-II IC lasers at 4.482 and 4.568 μm.

Microstructure of the GaSb-on-InAs heterojunction examined with cross-sectional scanning tunneling microscopy

We have investigated the atomic-scale morphology and composition of the GaSb-on-InAs heterojunction with cross-sectional scanning tunneling microscopy, and find a new “white-noise” component in the wave-vector-dependent roughness spectrum under epitaxial growth conditions routinely employed for type-II quantum well and interband cascade lasers. This phenomenon is associated with random substitutional defects at the interface whose concentration exceeds that due to bulk cross incorporation. We propose these defects originate from the thermodynamically favored but incomplete replacement of As by Sb at the InAs surface during anion exchange.

Cross-sectional scanning tunneling microscopy characterization of molecular beam epitaxy grown InAs/GaSb/AlSb heterostructures for mid-infrared interband cascade lasers

We have used cross-sectional scanning tunneling microscopy (STM) to examine two important aspects of material and interface quality in the mixed-anion InAs/GaSb/AlSb system under growth conditions similar to those presently employed for type-II quantum well and interband cascade lasers: (1) anion cross incorporation in the bulk (specifically, unintended substitution of As for Sb within the GaSb layers); and (2) the roughness spectrum at the common-anion AlSb-on-GaSb heterojunction. Two apparently different anion defects are noted in the GaSb layers, but the demonstration of a linear correlation between the bulk defect density observed with STM and the arsenic valve setting during antimonide layer growth clearly establishes background arsenic incorporation as the common origin for both of these defects. The roughness spectrum at the AlSb-on-GaSb interface displays a surprisingly short correlation length that is dominated by heterogeneity in the cation rather than anion sublattice. The relationship of these observations to fundamental materials-based performance limitations in type-II interband cascade lasers is briefly discussed.

Type-II and type-I interband cascade lasers

The authors propose two novel sources emitting in the mid-IR: type-II and type-I interband cascade lasers, and perform detailed gain calculations. High radiative efficiencies are expected, since the phonon processes which dominate relaxation in the intersub-band quantum cascade laser are effectively eliminated.

IR Sources and Modulators Based on InAs/GaSb/AlSb-Family Quantum Wells

ABSTRACTWe review recent applications of wavefunction engineering to the design of antimonide quantum heterostructures with favorable properties for infrared devices. Examples include electro-optical and all-optical modulators based on Г-L intervalley transfer, type-II quantum well lasers with enhanced gain per injected carrier, and type-II interband cascade lasers predicted to combine low thresholds and high output powers.