Electrical properties and transport mechanisms of InP/InGaAs HBTs operated at low temperature

Temperature studies of InAlAs–InGaAs–InAlAs double heterojunction bipolar transistors with no current blocking

“…Whereas, reduced back-injection of holes at lower temperature raises the current gain. We, in agreement with earlier studies on InP/InGaAs HBTs [3][4][5], observed that current gain limited by recombination in the base dominated other factors as the temperature was lowered. However, Hafizi et al [6] reported an increase of 6% in current gain when the temperature was reduced from 300 K to 123 K. Also, the carrier transport mechanism changes from thermionic/thermionic field emission to predominantly tunneling as the temperature is lowered.…”

“…Figure 4 (insets) shows idealities for base and collector current as the temperature is varied from 400 K to 77 K. For the values of temperature below 200 K, progressively large values of idealities for both base and collector current were observed. These large values of ideality factor can be explained on the basis of thermionic field emission theory, such that the current through the B-E junction at low temperature can be modeled by a low-temperature tunneling current through the Schottky barrier which is given by [3]…”

“…For example, Abid et al [4] reported a reduction of more than 60% in current gain for InP/InGaAs HBTs for a reduction in temperature from 290 K to 90 K, identifying tunneling to be the dominant transport mechanism across the base-emitter (B-E) junction to explain the higher ideality factors at low temperatures. Kruse et al [5] showed a reduction of 25% for temperature variations from 293 K to 33 K. Wang et al [3] reported a reduction of about 25% in current gain when the device temperature was reduced from 300 K to 9.4 K. They found deep-level traps-related recombination to dominate for temperatures ranging from liquid nitrogen (LN 2 ) to 240 K. However, similar studies of InAlAs/InGaAs HBTs are limited [6,7]. Hafizi et al [6] used coherent heterointerfaces for reflection and penetration (CHIRP) superlattice for the B-E interface and their work is limited to SHBTs.…”

“…This makes low-temperature studies of In 0.52 Al 0.48 As-In 0.53 Ga 0.47 As-In 0.52 Al 0.48 As HBTs very pertinent to understanding the various carrier transport mechanisms under cryogenic conditions in these devices. There have been several low-temperature studies of InP-In 0.53 Ga 0.47 As HBTs [3][4][5] showing varied degrees of current-gain dependence on temperature and identifying various transport mechanisms as being predominant in different temperature ranges. For example, Abid et al [4] reported a reduction of more than 60% in current gain for InP/InGaAs HBTs for a reduction in temperature from 290 K to 90 K, identifying tunneling to be the dominant transport mechanism across the base-emitter (B-E) junction to explain the higher ideality factors at low temperatures.…”

“…The combination of dipole doping and composite collector for the elimination of current blocking has only been reported for InP/InGaAs DHBTs both with [3] and without [9] quaternary alloys. In the case of InAlAs collector DHBTs, it has only been reported in conjunction with quaternary alloys (CHIRP superlattice and/or interface grading) [11,12].…”