Single chip bumping and reliability for flip chip processes

A new functional AIG^As/GaAs heterostruclure-cmitter bipolar transistor (HEBT) with a pseudomorphic inGaAs/GaAs quantum-well (QW) base slrueturc is presented. Due to the insertion of an InGaAs QW between the emitter-base (E-B) junction, the valence band discontinuity can be enhanced. The excellent transistor characteristics including a high current gain of 280 and a low offset voltage of [00 mV are obtained. In addition, an interesting multiple S-shaped negative differential resistance (NDR) phenomenon is observed under the inverted operation mode. This may be attributed to an avalanche multiplication and sequential two-stage barrier lowering effect. ((•; 1999 Elsevier Science Ltd. All rights reserved.