Suppression of the burn-in effect in InGaP/GaAs heterojunction bipolar transistors by constant period of voltage stress

Abstract

Effect of composite collector design on the breakdown behavior of InGaP/GaAs double heterojunction bipolar transistor J. Appl. Phys. 93, 605 (2003); 10.1063/1.1521513Analysis of collector-emitter offset voltage of InGaP/GaAs composite collector double heterojunction bipolar transistor Two significantly abrupt increases of dc current gain ͑␤͒ at the opposite extremes of base-emitter voltages (V be ) linked by a relatively slight increase of ␤ in the range of 1.25рV be р1.75 V are found in InGaP/GaAs heterojunction bipolar transistors ͑HBT's͒. It has been proved that the burn-in effect directly causes the second abrupt increase of ␤ occurring at V be Ͼ1.75 V instead of elsewhere. In addition, choosing V be Ͼ1.75 V, a higher base-emitter voltage results in a faster increase rate with improvement in current gain transient. Based on these observations, a constant period of voltage stress ͑CPVS͒ with V be ϭ2.0 V and V ce ϭ3.0 V for 5 min with a specific choice of V be Ͼ1.75 V ͑the voltage range corresponding to the second abrupt increase of ␤͒ is thus applied to promote the electrical performance of HBT's. After applying a CPVS, the burn-in effect is substantially suppressed without showing any second abrupt increase of current gain. Although the current measured under both reverse and forward biases is greatly reduced for the base-emitter junction, a CPVS slightly degrades the electrical properties of a base-collector junction. Also, it has been proved that bulk recombination, rather than the surface recombination current, the base contact recombination, or the space-charge recombination, is the dominant base current component causing the burn-in effect. The electrical improvement of the base-emitter junction is due to the annihilation of H-related traps in the base region after a CPVS. Once H Ϫ ions form, we propose that these ions are too fast to drift toward the base-collector junction under the reverse bias of the base-collector voltage. After migration through the extrinsic base region, H Ϫ ions are supposed to be trapped near the base-collector space region, which results in the degradation of the base-collector junction after a CPVS.

Burn-in effect in InGaP/GaAs HBT with intrinsically or extrinsically carbon doped base layer

“…V BE below 0.9 V, I B is mainly comprised of recombination current at emitter-base space charge region and it rises with annealing temperature for both devices. Therefore the increased base recombination current is due to degraded emitter-base junction after annealing and it causes β f decrease [21,22]. This effect is more pronounced on intrinsically-carbon-doped HBTs.…”