B.H. van Roy

Low-loss low-confinement GaAs-AlGaAs DQW laser diode with optical trap layer for high-power operation

A low-confinement asymmetric GaAs-AlGaAs double-quantum-well molecular-beam-epitaxy grown laser diode structure with optical trap layer is characterized, The value of the internal absorption coefficient is as low as 1.4 cm/sup -1/, while keeping the series resistance at values comparable cm with symmetrical quantum-well gradient index structures in the same material system. Uncoated devices show COD values of 35 mW//spl mu/m. If coated, this should scale to about 90 mW//spl mu/m. The threshold current density is about 1000 A/cm/sup 2/ for 2-mm-long devices and a considerable part of it is probably due to recombination in the optical trap layer. Fundamental mode operation is limited to 120-180 mW for 6.5-/spl mu/m-wide ridge waveguide uncoated devices and to 200-300 mW for 13.5-/spl mu/m-wide ones, because of thermal waveguiding effects. These values are measured under pulsed conditions, 10 /spl mu/s/l ms.

Sealing method of dry etched AlAs/GaAs top mirrors in vertical cavity surface emitting lasers

A versatile sealing process for AlAs layers is presented. This sealing prevents the AlAs layers of AlAs/GaAs top distributed Bragg reflectors from further undesired oxidation during the wet oxidation of the AlAs current constriction layers in vertical cavity surface emitting lasers. This method has been successfully applied to protect the etched pillars in top mirrors although those pillars were plasma dry etched.

Possibilities for polarisation control in vertical cavity surface emitting lasers for optical interconnects

VCSELs are expected to play an important role in short distance optical interconnects like fast reconfigurable or free-space interconnects. Besides the current modulation for data transmission, polarisation adds an extra parameter, which can be used for routing purposes. In this presentation we shall briefly describe the processing of intra-cavity contacted VCSELs including a seating method for the dry-etched DBR mesa. Asymmetric current injection in the active region was used. It reduces the current crowding problem along the edges of the oxide aperture. This has been confirmed using simple 2D electrical modelling. Moreover, asymmetric current injection showed the potential of stabilising the polarisation by introducing an anisotropy in the gain and loss resulting in a beam polarisation perpendicular to the direction at which the p- and n-contacts are placed.

Progress in reactive ion etching of epitaxial GaN

Reactive Ion Etching (RIE) of GaN epitaxially grown on (0001) sapphire substrate has been investigated using various chemistries based on SiCl/sub 4/, Ar and SF/sub 6/. Plasma deposited SiN/sub x/ is used for masking. We studied the influence of gas flow, pressure and RF-power on etch rate and morphology. High etch rates up to 150 nm/min can be obtained when using SIC/sub 4/:Ar:SF/sub 6/ (10:10:2 sccm) at an acceleration voltage of 370 Volts. Very smooth surfaces and good etch rates (/spl plusmn/100 nm/min) were obtained using the same chemistry at a lower RF-power of 105 Watts (DC-bias of /spl plusmn/290 V).