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High bandwidth 2- $\mu \text{m}$ wavelength surface normal p-i-n photodiodes using a high indium-content InGaAs strain-relaxed absorbing layer clad by p- and n-doped AlInGaAs layers are realized. A parabolic grading was used to relax the lattice constant from that of the InP substrate. We compare structures with different p-doping profiles and absorber thicknesses to achieve a 3-dB bandwidth of $\sim 10$ GHz while maintaining a photoresponsivity of 0.93 A/W. A clear opening of the 10-Gb/s eye pattern was obtained with an input power of −3.07 dBm. By temperature-control of the mesa passivation process, the device leakage was reduced to $0.52~\mu \text{A}$ at −5 V bias.

We demonstrate a shallow ridge waveguide, lumped element electroabsorption modulator (EAM) based on AlInGaAs multiple quantum wells, operating with input powers up to 8 dBm. The device was isolated between two DC controlled sections, using angled etched slots in the waveguide, minimizing optical feedback, while also providing 40-KΩ resistance between devices. The EAM uses a planar isolated pedestal contact with a benzocyclobutene bridge, allowing for a small contact footprint of just 0.024 mm2, while being suitable for flip-chip packaging. The parasitic capacitance was measured to be 19.6 fF, and the EAM has a f3dB bandwidth of 42 GHz.

We demonstrate ridge waveguide lasers based on AlInGaAs multiple quantum wells emitting at 1434 and 1541 nm on the same laser bar using quantum-well intermixing with dielectric capping layers. The internal quantum efficiencies are measured to be 61% and 72% and the internal losses are 49 and 23 cm-1 for lasers with intermixing promoted and inhibited, respectively. The characteristic temperatures are found to be approximately 50 K for lasers emitting around 1433 nm and 75 K for those emitting around 1541 nm.

The traveling-wave edge-coupled unitraveling-carrier (UTC) photodiode was designed and fabricated for zero-bias high-speed communication system application. A 40-μm-long 5-μm-wide UTC waveguide device demonstrated 13-GHz 3-dB bandwidth and up to 10-mA photocurrent without saturation in our measurement range under zero bias.

The authors have grown 997 nm vertical-cavity surface-emitting lasers with an offset between the wavelength of the cavity mode and the quantum well gain peak to improve high temperature operation, and with higher aluminum-content barriers around the active region to improve the carrier confinement. They fabricated lasers of 8-15 and 20- mu m diameters. The 8- mu m-diameter devices exhibited CW operation up to 140 degrees C with little change in threshold current from 15 degrees C to 100 degrees C, and the 20- mu m-diameter devices showed CW output power of 11 mW at 25 degrees C without significant heat sinking. >

Vertical cavity surface-emitting lasers originally designed for room temperature operation are operated at 77 K. At this temperature, the gain peak and the cavity mode do not overlap. However, due to joule heating, at high biasing levels they come back into alignment and high single-mode output powers and large modulation bandwidths are observed. >

High-yield, reliable electrically pumped index-guided vertical cavity lasers with diameters less than 4 microns have been fabricated using low resistance, alloyed, ring contact metallization. Existing metallization schemes used for bottom emitting vertical cavity lasers (VCLs) tend to be highly resistive, since the top metallization layer serves the dual purpose of mirror and electrical contact. This results in acceptable performance for large diameter devices, but poor performance for smaller devices that operate at higher current densities. Low resistance alloyed ring contacts have been developed for small bottom emitting VCLs that maintain the required optical properties while dramatically improving the electrical properties. >

Contacts have been made to p- and n-type layers on opposite sides of the active region within the cavity of an InGaAs vertical cavity surface emitting laser. The two concentric ring contacts allow all electrical connections on and emission from the top surface of a semi-insulating GaAs substrate. The design includes a novel current leveling layer to minimize current crowding effects. A high external quantum efficiency of 46% has been measured with maximum output powers up to 6 mW for a 15 /spl mu/m diameter device and threshold currents of 0.72 mA for a 7 /spl mu/m diameter laser. >

Modifications to the epitaxial growth of vertical-cavity surface-emitting laser (VCSEL) material have recently led to improved characteristics. By offsetting the quantum-well gain peak from the cavity mode, and implementing lower barrier p-type Al/sub 0.67/Ga/sub 0.33/As/GaAs DBR mirrors with parabolic interface gradings, better high-temperature operation and lower voltages have been achieved. These effects combine to yield a peak wall plug efficiency of 17.3% for room temperature, CW operation. >