Influence of V/III Ratio of Carbon-Doped p-GaAs on Current Gain and Its Thermal Stability in InGaP/GaAs Heterojunction Bipolar Transistors

Abstract

The influence of the V/III ratio of carbon-doped p-GaAs on current gain and its thermal stability in InGaP/GaAs heterojunction bipolar transistors (HBTs) was studied. We have grown p-GaAs bulk layers and InGaP/GaAs HBTs at a growth temperature of 620 °C with V/III ratios between 0.35 and 25 employing CBrCl3 as a carbon source using a mass production metal–organic chemical vapor deposition instrument. We have found that a V/III ratio of 0.7 showed high current gain; however, the V/III ratio of 0.7 degrades under thermal annealing. On the other hand, a V/III ratio of 25 represents a significant improvement in thermal stability. Time resolved photo-luminescence revealed that the lifetime for the V/III ratio of 0.7 decreased with increasing annealing time, while the lifetime for the V/III ratio of 25 remained unchanged. These results suggest that current gain degradation for the V/III ratio of 0.7 is caused by the creation of recombination centers in the base layer.

High current gain stability of carbon-doped p-GaAs in InGaP/GaAs heterojunction bipolar transistors

“…For the V/III ratio of 0.7, the current gain strongly depends on base sheet resistance. This is due to creation of recombination centers in the base layer as judged from time-resolved photoluminescence at RT [13]. For the V/III ratio of 25, current gain kept almost constant regardless of base sheet resistance in this range.…”

“…1 should be attributed to the C 2 -H complex. We suggest the C 2 -H complex in the V/III ratio of 0.7 cause defect centers when annealed above 550 1C [13]. As a result, recombination center in the base layer is created, which leads to current gain degradation.…”

“…InGaP-HBT structure was described in our separate paper [13]. A 70 nm carbon-doped p-GaAs base layer was grown at 620 1C with V/III ratios of 0.7 and 25 changing the AsH 3 flow rate under a constant TMG flow rate.…”

“…We recently reported the MOCVD of p-GaAs bulk layers and InGaP/GaAs HBTs at growth temperature of 620 1C with various V/III ratios between 0.35 and 25 [13], employing CBrCl 3 as a carbon source [14]. We found that a V/III ratio of 0.7 showed higher current gain than a V/III ratio of 25; however, the current gain of the V/III ratio of 0.7 readily degraded when annealed above 550 1C.…”

Hydrogen-related defects in InGaP/GaAs heterojunction bipolar transistors

“…However, heavy carbon doping over 10 19 cm À3 by metal-organic chemical vapor deposition (MOCVD) incorporates large amounts of hydrogen atoms in the base layer [3,4]. The presence of hydrogen atoms affects the device performance [5][6][7][8][9][10][11]. The current gain increases and stabilizes after a current injection for a few seconds, which is called short-term gain-drift [5][6][7][8][9].…”