The 3 to 4 μm range had long appeared inaccessible to quantum well lasers made on GaSb. Despite having excellent performance in the 2 to 3 μm range, GaInAsSb/AlGaAsSb quantum well lasers rapidly show their limits when crossing the 3 μm barrier (the highest wavelength reached with such a device was 3.04 μm under cw operation at 20°C). This situation was all the more regrettable because several gases have their strongest absorption lines in the 3 to 4 μm range: methane, for example, has a peak of absorption at 3.26 μm overhanging a weaker peak at 2.31μm by a factor 40. Works carried out in the University of Munich in 2005 gave new hopes to the world of laser diode spectroscopy. By replacing the quaternary AlGaAsSb barrier by a quinary AlGaInAsSb barrier, researchers were able to reach laser operation at 3.26 μm and room temperature in the pulsed mode. Since then, several teams have engaged in the objective of reaching cw operation at room temperature with such structures. We will give an insight into the phenomena responsible for the increase of threshold current with growing wavelength. Finally, we will present results obtained with a monomode DFB laser diode emitting at 3.37 μm having a threshold current of 140 mA at 18°C.

We have investigated specifically designed GaSb-based laser diodes epitaxially grown on a Si substrate. We demonstrate continuous-wave operation of these laser diodes emitting near 2 μm up to 35 °C with several mW/facet output powers, limited by our experimental setup. Our results open the way to direct monolithic III-V/Si integration.

Widely-tunable monolithic two-section lasers emitting at around 3.3 mu m have been developed. The devices are based on GaInAsSb quantum wells with quinary AlGaInAsSb barrier layers. Tuning is achieved by adjusting the currents injected into two segments with lateral binary superimposed gratings. Counter-directional current-tuning of the segments resulted in wavelength channel switching, co-directional current-tuning in wavelength tuning of a channel. The typical tuning range of the devices is around 23 nm. High-sensitivity measurements indicate that sidemode suppression ratios are usually around 45 dB.

Distributed feedback (DFB) laser diodes based on the concept of lateral metal gratings fabricated on type-I quantum well GaInAsSb/AlGaInAsSb material are presented. Monomode emission in the 3.4 mu m wavelength range was achieved for the first time for a GaSb based DFB laser diode. Excellent sidemode suppression ratios beyond 30 dB are demonstrated in combination with a modehop-free tuning range around 8.5 nm. Using a specially developed polymer-free DFB processing route allowing improved heat dissipation, laser operation in continuous-wave mode was observed at temperatures up to around 20 degrees C.

The material system comprising GaSb, InAs, AlSb and their related alloys are an impressive toolbox for device designers, as they offer a very large choice of band-gaps and band offsets. Molecular beam epitaxy (MBE) and device processing have been improving quickly over recent years, allowing the fabrication of high performance devices as quantum cascade lasers, mid-infrared (MIR) edge emitting and surface emitting lasers, superlattice infrared photodetectors, but also very high speed / low consumption AlSb/InAs field effect transistors. Efforts have been made to monolithically grow these devices onto larger and cheaper substrates like GaAs and Si, to improve the yield / decrease the cost of this technology and possibly integrate the devices with CMOS technology. We recently fabricated a 2.3 μm edge emitting laser grown by MBE on a Si substrate, and demonstrated roomtemperature pulsed operation. Lasers emitting at this wavelength are of particular interest for gas sensing. Challenges to further improve the device include the substrate preparation, optimization of the nucleation layer quality, but also the conduction band engineering in order to facilitate the electronic transport at the Si/III-Sb interface.

We report on the first Sb-based type-1 laser grown on GaAs substrate operating continuous-wave around 2.2 mu m at room-temperature. The device was grown using solid-source molecular beam epitaxy and comprised two GaInAsSb quantum-wells embedded in AlGaAsSb barriers. Despite the large lattice-mismatch, a good crystalline quality was obtained, and processed devices operated continuous wave up to 50 degrees C, with threshold current densities in the range of 1.5 to 2.2 kA/cm(2). An optical output power of 3.7 mW was obtained at 20 degrees C. (C) 2009 Optical Society of America

GaSb based EP-VCSELs were fabricated. Room temperature lasing has been achieved from 2.3 mum up to 2.63 mum which is the longest wavelength VCSELs reported.

In this paper, we studied wet chemical etching fabrication of the InAs/GaSb superlattice mesa photodiode for the mid-infrared region. The details of the wet chemical etchants used for the device process are presented. The etching solution is based on orthophosphoric acid (H3PO4), citric acid (C6H8O7) and H2O2, followed by chemical polishing with the sodium hypochlorite (NaClO) solution and protection with photoresist polymerized. The photodiode performance is evaluated by current-voltage measurements. The zero-bias resistance area product R(0)A above 4 x 10(5) Omega cm(2) at 77 K is reported. The device did not show dark current degradation at 77 K after exposition during 3 weeks to the ambient air.

Electrically-pumped GaSb-based vertical-cavity surface-emitting lasers emitting up to 2.63 mu m at room temperature are reported. The whole structure was grown monolithically in one run by solid-source molecular beam epitaxy. This heterostructure is composed of two n-doped AlAsSb/GaSb DBRs, a type-I GaInAsSb/AlGaAsSb multiquantum-well active region and an InAsSb/GaSb tunnel junction. A quasi-CW ( 1 mu s, 5%) operation was obtained at room temperature for 35 mu m-diameter devices with threshold current of 85 mA.

Laser diodes based on 4ML InAs/3ML GaSb/1ML InSb/3ML GaSb short-period superlattices (SPSLs) for emission in the 3-3.5 mu m wave-length range have been investigated. Lasing is demonstrated up to 300 K in pulsed conditions and up to 200 K under continuous wave operation. Laser emission is centred at similar to 3.3 mu m, a technologically very important wavelength. The results demonstrate the potential of these new active zones for mid-IR laser diodes.

We report the growth conditions and operations of electrically pumped monolithic Sb-based type-I quantum-well vertical cavity surface emitting lasers (VCSELs) emitting above 2.2μm. The structures were grown on (001)-GaSb substrates by molecular beam epitaxy (MBE) and are made of two N-type GaSb/AlAsSb Bragg reflectors, a GaInAsSb/AlGaAsSb multiquantum-well active region and an InAsSb/GaSb tunnel junction. Growth conditions have been optimized for each target wavelength. Laser emission in CW up to 293K at 2.3μm and in pulsed regime at 2.52μm at room temperature (RT) is demonstrated. These are the longest wavelength achieved with electrically pumped VCSELs to date.

Mid-infrared laser diodes are highly attractive sources for gas spectroscopy applications due to the presence of strong absorption lines of many gaseous species in this spectral range. Particularly, the 2.3 – 3.3 µm wavelength range contains strong absorption lines of some pollutants as CH4, NH3 or HF while CO2 and H2O interference absorption lines are very low which renders possible the highly selective and sensitive detection of these pollutants. Vertical-cavity surface-emitting lasers (VCSELs) appear especially well adapted to be used as laser sources for absorption spectroscopy due to several intrinsic characteristics that they offer. The low threshold, single-mode operation, the circular output beam with low divergence are only some of their well-known advantages.

We report on a GaSb-based type-I laser structure grown by molecular beam epitaxy on a (001) silicon substrate. A thin AlSb nucleation layer followed by a 1 μm thick GaSb buffer layer was used to accommodate the very large lattice mismatch existing with the silicon substrate. Processed devices with mesa geometry exhibited laser operation in pulsed mode with a duty cycle up to 10% at room temperature.

Room-temperature continuous-wave (CW) operation of GaSb-based monolithic microcavity vertical-cavity surface-emitting lasers operating near 2.3 mum is presented. These devices were composed of two n-doped AlAsSb-GaSb Bragg mirrors, a type-I GaInAsSb-AlGaAsSb multiquantum-well active region, and an n++-InAsSb/p++-GaSb tunnel junction. CW laser operation was observed up to 294 K. A CW threshold current density as low as 1.1 kA ldr cm-2 was obtained at 284 K for 60-mum-diameter devices (20-mum-diameter emitting area).

An all-epitaxial monolithic vertical cavity surface emitting laser grown on GaSb substrate is presented. The structure is composed of two n-doped AlAsSb/GaSb distributed Bragg reflectors, a type-I GaInAsSb/AlGaAsSb multi-quantum-well active region and a tunnel junction. Quasi continuous-wave laser operation is demonstrated at 2.3 mu m up to room temperature. Threshold current densities of 0.8 and 0.6 kA/cm(2) are obtained at 300 and 280 K for 80 mu m-diameter devices (1 mu s pulses, 10% duty cycle). A peak output optical power of 2 mW was achieved at 280 K.

The first electrically-pumped GaSb-based vertical cavity surface emitting lasers emitting above 2.5 mu m at room temperature are reported. This monolithic all-epitaxial structure is composed of two n-doped AlAsSb/GaSb DBRs, a type-I GaInAsSb/AlGaAsSb multi-quantum-well active region and an InAsSb/GaSb tunnel junction. Devices with a diameter of 30 mu m operate in quasi-CW ( 1 mu s, 5%) at 2.52 mu m above 300 K. A minimum threshold current of 4.7 kA/cm(2) in pulsed operation (100 ns, 0.5%) was obtained at 251 K with these devices.

Monolithic microcavity GaSb-based VCSELs emitting above 2.2 mu m in Continuous Wave Regime at Room Temperature are reported. For 60 mu m diameter devices, a density threshold of 1.1 kA/cm(2) was measured at 290K.

The growth by molecular-beam epitaxy of novel electrically pumped type-II multi-quantum well (MQW) Sb-based laser diodes in which only the holes are quantum confined was studied. These laser structures were fabricated on (001) GaSb substrates. In the MQW region, radiative recombinations originate from InGaSb hole wells embedded in InGaAsSb barriers lattice matched to GaSb. Two different laser structures were developed. The first one exhibited a well/barrier periodicity that was too short, which led to a laser emission near 2.65μm originating from the waveguide rather than from the wells. With an improved well/barrier periodicity, the second structure exhibited laser emission up to 243K at 2.93μm in the pulsed regime (200ns, 5kHz). In this case, the laser photons were effectively produced by the hole-well active region. A minimum threshold of about 12.8kA/cm2 at 80K combined with a T0 around 70K have been measured from this second structure.

This paper is dedicated to the study of electrical and optical properties of four different doped 21.5 pairs AlAsSb/GaSb distributed Bragg reflectors lattice-matched to GaSb and designed for the fabrication of electrically pumped VCSELs emitting around 2.3 µm. Three different doping profiles have been carried out: n-bulk doping, n-delta doping and p-bulk doping. An n-type bulk doped Bragg mirror with step composition at GaSb/AlAsSb interfaces was also tested. The n-type bulk doped sample with sharp interfaces exhibited the best electrical properties, a voltage drop per pair of 25 mV and a specific resistance of 1 × 10−4 Ω cm2 at 1 kA cm−2. Moreover, optical losses as low as 5–10 cm−1 have been measured for n-type doped mirrors.