D.A. Buell

88 °C, continuous-wave operation of apertured, intracavity contacted, 1.55 μm vertical-cavity surface-emitting lasers

We demonstrate a lattice-matched 1.55 μm vertical-cavity surface-emitting laser operating continuous wave up to 88 °C. The laser employs AlAsSb-based mirrors, which provide high reflectivity and lattice matching to InP. The poor electrical and thermal conductivity of these mirrors is circumvented by utilizing an InP double-intracavity contacted structure. Benefits of the intracavity contacts are addressed by comparing the characteristics with the alternative contact scheme where current is injected through the Sb-based mirrors. Current and optical confinement is provided by an undercut aperture. The device shows a threshold current of 800 μA, a differential efficiency of 23%, and a maximum output power of over 1 mW at 20 °C.

InP-based all-epitaxial 1.3-μm VCSELs with selectively etched AlInAs apertures and Sb-based DBRs

We report, for the first time, InP-based all-epitaxially grown 1.3-/spl mu/m vertical-cavity surface-emitting lasers with lattice-matched Sb-based distributed Bragg reflectors and AlInAs etched apertures. The minimum threshold current and voltage under pulsed operation were 3 mA and 2.0 V, respectively. The thermal impedance was as low as 1.2 K/mW without heat sinking. Implementation of the AlInAs etched aperture was quite effective in improving the injection efficiency and reducing the internal loss, resulting in improved differential efficiency.

Molecular-beam epitaxy growth of high-quality active regions with strained InxGa1−xAs quantum wells and lattice-matched AlxGayIn(1−x−y)As barriers using submonolayer superlattices

Submonolayer superlattices (SMS) of Ga0.47In0.53As/InAs/Ga0.47In0.52As and Ga0.47In0.53As/Al0.48In0.52As were used for the growth of strained quantum wells (QWs) and lattice-matched barriers, respectively, in the 1.55 μm active region. QWs grown with different compressive strains show excellent room-temperature photoluminescence, demonstrating the versatility of this technique. State-of-the-art current thresholds are reported for the broad-area lasers fabricated using the SMS active region.

Al0.95Ga0.05As0.56Sb0.44 for lateral oxide-confinement layer in InP-based devices

We report a lateral oxide-confinement layer for InP-based devices using lattice-matched AlGaAsSb. The confinement-layer-induced excess loss at different widths was extracted after de-embedding the losses due to carrier diffusion, nonradiative recombination, and changes in internal injection efficiency. The results show that AlGaAsSb oxide acts as an excellent confinement layer, and shows no excess loss down to a width of 4 μm.

Continuous-wave operation of 1.55-μm vertical-cavity surface-emitting laser with digital-alloy active region using submonolayer superlattices

For the first time, a digital-alloy active region (DAAR) consisting of submonolayer superlattices was used in a 1.55-/spl mu/m vertical-cavity surface-emitting laser. The device showed continuous-wave operation with a room-temperature threshold current (I/sub th/) of 1.2 mA, maximum output power (P/sub max/) of 0.26 mW, and a differential quantum efficiency (/spl eta//sub d/) of 21%. These results indicate that the DAAR is at least as efficient as the analog-alloy active region and provides much better control of alloy composition and strain.

InP-based 1310-1550 nm lattice-matched VCSELs

We have reviewed the recent research carried out to realize all-epitaxial VCSELs at long wavelengths. Shortcomings of the InP materials system were overcome by the use of AsSb-based alloys for DBRs and multiple active regions to combat low gain materials. The inclusion of InP spreading layers was seen to greatly improve the thermal properties of the devices. Aperturing schemes were presented which will improve these already world-class devices.

Lattice-matched Al0.95Ga0.05AsSb oxide for current confinement in InP-based long wavelength VCSELs

We examine, for the first time, Al 0.95 Ga 0.05 AsSb-oxide as the lateral current confining layer for InP-based optoelectronic devices including vertical cavity surface emitting lasers. In this paper, Al0.95Ga0.05AsSb-oxide confined broad area edge emitting lasers were used to study current confinement and optical loss. Results show that the threshold current density scales effectively down to a confining layer width of 6.5 μm and the differential efficiency remains unchanged down to 4 μm, indicating no aperture induced excess loss. This suggests that thin AlGaAsSb layers, at low oxidation temneratures. mav eet oxidized homogeneously without leaving metallic-Sb behind.

Current status of epitaxial 1.31-1.55 /spl mu/m VCSELs on InP

We have reviewed the recent research carried out to realize all-epitaxial VCSELs at long wavelengths. Shortcomings of the InP materials system were overcome by the use of AsSb-based alloys for DBRs and multiple active regions to combat low gain materials. The inclusion of InP spreading layers was seen to greatly improve the thermal properties of the devices. Two apertures were developed for the optical and current confinement. Careful placement of these apertures is expected to improve the VCSEL performance considerably.

Lattice-matched Al/sub 0.95/Ga/sub 0.05/AsSb oxide for current confinement in InP-based long wavelength VCSELs

InP-based active region is the material-of-choice for long wavelength VCSELs. In order to develop low threshold VCSELs, it is essential to have lateral current- and optical-confining apertures. The use of AlAs oxide-defined apertures has resulted in reduced optical loss of short wavelength VCSELs grown lattice-matched to GaAs. On the other hand, the InP lattice-matched analogue, namely AlInAs (TA,), is not an ideal candidate for oxide apertures because of its slow oxidation rate and high oxidation temperature. Though the efforts to increase the oxidation rate by using strained (T/sub As//AlAs) and strain-compensated (AlAs/InAs) superlattices have shown improvement in the oxidation rate and current confinement, it would be desirable to have a lattice-matched confinement layer which can be oxidized at much lower temperatures to increase the process reliability and yield. In this paper, we have studied the InP lattice-matched Al/sub 0.95/Ga/sub 0.05/AsSb (Q/sub Sb/) oxide layer for current confinement.

1.55 /spl mu/m, double-intracavity contacted, InP-lattice-matched VCSELs

We demonstrate a 1.55 /spl mu/m, double-intracavity contacted VCSEL operating at room temperature under CW. The whole structure is completely lattice-matched to InP and grown at single step. A VCSEL with a 14 /spl mu/m diameter current aperture shows the threshold current of 2.0 mA and the maximum output power of 480 /spl mu/W at 25/spl deg/C, and it operates up to 60/spl deg/C. The threshold voltage and differential resistance are 1.3 V and 40 /spl Omega/, respectively, for a 10 /spl mu/m aperture VCSEL.