Minority carrier properties of carbon-doped GaInAsN bipolar transistors

Abstract

We have developed an InGaP/GaInAsN/GaAs double heterojunction bipolar transistor technology that substantially improves upon existing GaAs-based HBTs. Band-gap engineering with dilute nitride GaInAsN alloys is utilized to enhance a variety of key device characteristics, including lower operating voltages, improved temperature stability and increased RF performance. Furthermore, GaInAsN-based HBTs are fully compatible with existing highvolume MOVPE and IC fabrication processes. While poor lifetimes have limited the applicability of dilute nitride materials in photovoltaic applications, we achieve minority carrier characteristics that approach those of conventional GaAs HBTs. We have found that a combination of growth algorithm optimization and compositional grading are critical for improving minority carrier properties in GaInAsN. In this work, we characterize the impact of both carbon and nitrogen doping on minority carrier lifetimes in GaInAsN base layers. Minority carrier lifetimes are extracted from direct measurements on bipolar transistor device structures. Specifically, lifetime is derived from the DC current gain, or β, taken in the bias regime dominated by neutral base recombination. Lifetimes extracted using this technique are observed to be inversely proportional to both carbon and nitrogen doping. As with conventional C-doped GaAs HBTs, current soaking (i.e. burn-in) is found to have a significant impact on GaInAsN HBTs. While we can replicate poor as-grown lifetimes consistent with those reported in photovoltaic dilute nitride materials, our best material to date exhibits nearly 30× higher lifetime after current soaking.

Carbon-nitrogen molecules in GaAs and GaP

“…[8][9][10][11][12][13][14] It is therefore very important that defects and impurities in these alloys are studied in detail. Carbon is a common impurity in various growth techniques 15,16 and sometimes, it is intentionally used as a p-type dopant; [17][18][19][20] complex formations between C and N could therefore be an important issue. Recently, Ulrici and Clerjaud 21 observed a sharp local vibration mode at 2087 cm −1 ͑at T =7 K͒ in GaP and a similar mode in GaAs.…”

Collection of photocarriers in Ga/sub 1-x/In/sub x/N/sub y/As/sub 1-y/ solar cells

“…Although these are very rough estimates, it is clear that 1) the observed µτ product varies with field, and 2) the ~0.1 V/µm fields observed in the best GaInNAs samples are expected to lead to field-aided collection. Evidence of field-aided minority-carrier transport in transistors has been reported by Welser, et al [14]. Aqueous junction In summary, we have observed that the device structure is more important than the growth conditions for high-performance GaInNAs cells.…”

Challenges to III-V Epi Growth for Increased Performance and Functionality Required in Advanced Wireless Devices

“…Therefore, the impact of base doping on minority carrier lifetime must be separated. These factors can be separated through the expression for average velocity where v is average velocity, N is average base doping, w is base width, and β is DC gain (9,10). The change in average velocity versus X L is plotted in Figure 2 for the three sets of dopant graded base layers, where X L is the thickness of the lower doped portion of the base adjacent to the collector (i.e.…”