S. Rapp

Experimental demonstration of a multifunctional long-wavelength vertical-cavity laser amplifier-detector

We report on the first experimental realization of a multifunctional long wavelength /spl lambda/=1.5-/spl mu/m InGaAsP MQW vertical cavity laser amplifier-photodetector. An optical gain of up to 18 dB and a voltage responsivity of 160 V/W is demonstrated.

All-Epitaxial Single-Fused 1.55 µm Vertical Cavity Laser Based on an InP Bragg Reflector

We have realised an all-epitaxial 1.55 µm vertical cavity laser by employing a single wafer-fusion step. The laser structure is fabricated by fusing a 32-period p-doped (C) AlGaAs/GaAs top mirror onto a half-cavity structure consisting of a 50-period n-doped (Si) GaInAsP/InP bottom mirror and a 9 quantum well GaInAsP-active material. Laser mesas are fabricated using a wet etching procedure for the top mirror. The top mirror also contains an AlAs layer for oxidation for current confinement. The lasers operate pulsed at temperatures up to 40°C and at pulse lengths of 10 µs up to 5°C. The minimum threshold current density at room temperature is 1.8 kA/cm2 for a device diameter of 55 µm. Compared to nonoxidised laser diodes, the threshold current is markedly decreased in oxidised laser diodes.

Systematics of Electrical Conductivity across InP to GaAs Wafer-Fused Interfaces

We report on the electrical and compositional characterization of wafer-fused isotype heterojunctions between Zn-, C- or Si-doped GaAs and Zn- or Si-doped InP. The junctions were characterized by current-voltage and secondary ion mass spectrometry (SIMS) measurements. It is demonstrated that very low-resistive junctions can be obtained in each case, but also that there is a strong influence from the detailed sample structure and processing conditions. SIMS was used to monitor the doping concentration across the interface as well as the impurity concentrations of oxygen, carbon and iron.

Experimental demonstration of a multifunctional long wavelength vertical cavity laser amplifier-detector (VCLAD)

We report on the first experimental realisation of a multifunctional long wavelength /spl lambda/=1.5 /spl mu/m vertical cavity laser amplifier-detector.

High speed modulation characteristics of long wavelength vertical cavity lasers based on an integrated InP Bragg reflector

The high-speed performance of 1.55 /spl mu/m GaInAsP MQW vertical cavity lasers based on a 50-period GaInAsP-InP bottom mirror operating continuous-wave at low temperature is presented. The maximum small-signal modulation bandwidth was limited by parasitics to 3.4 GHz.

Analysis of temperature effects on 1.55 /spl mu/m vertical-cavity lasers

Long-wavelength vertical-cavity surface-emitting lasers (VCSELs) are strongly temperature sensitive. Room-temperature continuous-wave operation of those VCSELs has been achieved only recently. Here, we investigate pulsed operation of 1.55 /spl mu/m VCSELs with strain-compensated InGaAsP/InP multi quantum wells (MQWs). A comprehensive two-dimensional VCSEL model is used to investigate those temperature effects. The optical gain is obtained from kp band structure computations and it includes many-body effects. Temperature dependent loss mechanisms like Auger recombination, carrier leakage, and intervalence band absorption are considered. Careful adjustment of material parameters led to an excellent agreement with a large variety of measurements.

Temperature-dependent performance of 1.55 /spl mu/m vertical-cavity lasers with InGaAsP/InP bottom mirror

We have fabricated and evaluated a long-wavelength vertical-cavity laser (VCL) based on an epitaxially integrated InP distributed Bragg reflector (DBR) under continuous wave (CW) and pulsed conditions. We conclude that, for an InP-DBR-down configuration, the high temperature performance is limited by the heat conductivity of the bottom mirror. The highest operating temperature for CW and pulsed condition is 17/spl deg/C and 101/spl deg/C respectively, indicating a substantial self-heating for CW. To investigate the prospect for improved performance in other mounting configurations, we have applied a two-dimensional finite element analysis to the heat transfer problem. It is suggested that for top-side-down mounting with the AlGaAs/GaAs DBR closest to the heat sink, a performance comparable to that of so called double-fused VCLs could be possible.

Long wavelength vertical cavity lasers

We report on three novel vertical cavity laser (VCL) structures for 1.55μm operation. Two of the VCL structures utilize an n-type GaInAsP/InP Bragg mirror combined with an Al(Ga)As/GaAs mirror using either wafer-fusion or metamorphic epitaxial growth. The third VCL employs two wafer fused AlGaAs/GaAs mirrors, in which lateral current confinement is obtained by localized fusion of the p-mirror. All three VCLs use strained GaInAsP quantum wells as active material and achieve continuous-wave (CW) operation at room-temperature or above. The single fused VCL operates up to 17°C and 101°C in continuous-wave and pulsed mode, respectively. The monolithic VCL-structure with a metamorphic GaAs/AlAs n-type mirror uses a reversed biased tunnel junction for current injection. This laser achieves record high output power (1mW) at room temperature and operates CW up to 45°C. The double fused VCLs with a 10×10μm 2 active area operate CW up to 30°C with threshold current as low as 2.5mA and series resistance of 30 Ohms. The emission spectra exhibit a single lasing mode polarized with 30 dB extinction ratio and a spectral linewidth of 150 MHz.

Systematics of electrical conductivity across InP to GaAs wafer fused interfaces

We report on the electrical and compositional characterization of wafer fused isotype heterojunctions between Zn, C or Si doped GaAs and Zn or Si doped InP. The junctions were characterized with current-voltage and secondary ion mass spectrometry (SIMS) measurements. It is demonstrated that very low-resistive junctions can be obtained in each case, but also that there is a strong influence from the detailed sample structure and processing conditions. SIMS was used to monitor the doping concentration across the interface as well as the impurity concentration of oxygen, carbon and iron.

All epitaxial single-fused 1.55 /spl mu/m vertical cavity laser based on an InP Bragg reflector

We have realised all epitaxial 1.55 /spl mu/m vertical cavity lasers by employing a single wafer-fusion step. The laser structure is fabricated by fusing a 32 period p-doped (C) AlGaAs/GaAs top mirror to a half-cavity structure consisting of a 50 period n-doped (Si) GaInAsP/InP bottom mirror and 9 QW GaInAsP-active material. Laser mesas are fabricated using a wet etching procedure for the top mirror. The top mirror also contains an AlAs layer for oxidation for current confinement. The lasers operate pulsed for temperatures up to 40/spl deg/C and at pulse lengths of 10 /spl mu/s up to 5/spl deg/C. The minimum threshold current density at room temperature is 1.8 kA/cm/sup 2/ for a device diameter of 55 /spl mu/m. Compared to non-oxidised laser diodes, the oxidation decreases the threshold currents significantly.