A method of manufacturing a heterojunction bipolar transistor comprising the steps of forming a first semiconductor layer of a first conductivity type (108, 110) as a collector on a semiconductor substrate (112), forming a second semiconductor layer of a second conductivity type (106) as a base on the first semiconductor layer, forming a third semiconductor layer of the first conductivity type (100, 102, 104) as an emitter on the second semiconductor layer, the third and second semiconductor layers constituting a heterojunction, selectively forming a first mask on the third semiconductor layer, ion-implanting ions of an impurity of the second conductivity type Into the resultant structure using a first mask, thereby forming an external base region (118a) of the second conductivity type extending to the second semiconductor layer, forming a second mask on a side wall of the first mask, and ion-implanting a predetermined material into the resultant structure using the first and second masks, thereby forming a high-resistance layer (128) for isolating the external base region in self-alignment with the emitter.

Method of manufacturing heterojunction bipolar transistor

A new type of optical fiber with a twin-core is proposed exhibiting good birefringence properties. The theoretical analysis of the structure is performed using a finite difference method based on a vector potential formulation. The birefringence of the twin-core fiber is compared to that of an elliptical step-index guide, showing the advantage of the former. It also appears that the normalized birefringence parameter currently used for the elliptical fiber does not apply in the monomode region.

Birefringence properties of twin-core fibers by finite differences

Polarization-maintaining single-mode fibers will find application in acoustooptic sensors and fiber gyroscopes. In this study both stress-induced birefringence and elliptical core polarization-maintaining single-mode fibers were developed and evaluated. The two fiber types were compared in terms of core dimension, numerical aperture, attenuation, and beat length, a measure of the polarization maintenance. For comparative beat length values the stress-induced birefringence fibers had lower attenuation and larger core diameter than the elliptical core fibers.

Polarization-maintaining single-mode fibers

A 10W IMPATT Diode Amplifier for X-Band Communication Systems

Schottky-barrier hi-lo GaAs Impatt diodes with Ti-Pt-Au contacts have been fabricated for the 10.7?11.7 GHz band. At 180°C junction temperature rise the diodes have produced over 5 W of output power and up to 24% efficiency from an 11 GHz oscillator. Initial life tests show potential for high reliability.

P.A. Leigh

Papers

High-power 11 GHz GaAs hi-lo Impatt diodes with titanium Schottky barriers