Measurements of the InGaAs hole impact ionization coefficient in InAlAs/InGaAs pnp HBTs

Abstract

The hole multiplication factor in pnp InAlAs/InGaAs single heterojunction bipolar transistors (HBTs) has been measured as a function of the base-collector bias. The hole impact ionization coefficient beta (p) has been estimated taking into account the Early effect, I-CBO, and thermal effects. Numerical corrections for dead space were made. The importance of considering second order effects is highlighted, showing that rough approximations can lead to an overestimation of the coefficient beta (p). At low electric fields, the extracted coefficient agrees with the most recent photomultiplication measurements available in the literature, At high electric fields, hole impact ionization coefficient is estimated up to values previously not reported in the literature (beta (p) approximate to 10(4) cm(-1))

Field dependence of impact ionization coefficients in In/sub 0_53/Ga/sub 0_47/As

“…Although the results in [1] and [2] agree at higher fields, the values of are in disagreement with those in [5] and [6] for fields below 200 kVcm . By contrast, the recent HBT measurements of [7], [8], which agree qualitatively with those reported in [5], [6] did not show this low field impact ionization.…”

“…Although the more recent HBT measurements [1], [2], [7], [8] covered a wider electric field range than the earlier photomultiplication measurements [4]- [6], and could not be measured on the same HBT layer, and the interpretation relied on the sim- plifying assumption that . Furthermore, these HBT results were measured on only one layer in each investigation so that errors in determining fields and multiplication factors could not easily be detected.…”

“…More critically, these HBT-based results relied on measuring the dc collector current in which leakage current was not easily distinguished from that induced by impact ionization. Most of the measurements in the previous works also required correction, either for depletion-edge movement (in the photomultiplication measurements [4]- [6]) or for Early effect (in the HBT measurements [7], [8]), introducing further uncertainties in the multiplication factors and, hence, in the ionization coefficients, especially at low fields. The uncertainties in and can have a significant impact on the design of HBT structures.…”

“…The uncertainties in and can have a significant impact on the design of HBT structures. For example, calculations using the Ebers-Moll equations [9] show that a 20% uncertainty in and (less than the spread between results of [4]- [8]) will result in a 10% spread in the collector-emitter breakdown voltage of a common-emitter configured HBT with a 0.3-m-thick collector and a transistor gain of 30.…”

Excess noise measurement in In/sub 0.53/Ga/sub 0.47/As

“…Ng et al [4] reported high values of at fields below 200 kV cm corroborating those previously reported by [2], [3] deduced from measurements on n-p-n HBTs with In Ga As base and collector layers. derived from p-n-p HBT measurements [13], [14] and photomultiplication measurements [4], [10]- [12] did not show any low field ionization, but Ng et al [4] reported marginally lower values of . The determination of at low field in p-i-n and HBT structures is fraught with complications.…”