Chemical vapour deposition of coatings

We report on the physical operation and performance of MOCVD-grown abrupt heterojunction InP/GaAs/sub 0.51/Sb/sub 0.49//InP double heterojunction bipolar transistors (DHBTs). In particular, the effect of the InP collector thickness on the breakdown voltage and on the current gain cutoff frequency is assessed and a f/sub T/ of 106 GHz is reported for a DHBT with a 400 /spl Aring/ base and a 2000 /spl Aring/ InP collector with a BV/sub CEO/ of 8 V. We show that InP/GaAsSb/InP DHBTs are characterized by a weak variation of f/sub T/ as a function of temperature. Finally, we also demonstrate that high maximum oscillation frequencies f/sub MAX/>f/sub T/ can be achieved in scaled high-speed InP/GaAsSb/InP DHBTs, and provide estimates of the maximum cutoff frequencies achievable for this emergent but promising material system. Recent results on improved structures validate our performance predictions with cutoff frequencies well beyond 200 GHz.

InP/GaAsSb/InP double HBTs: a new alternative for InP-based DHBTs

The high-frequency performance of small scale InP/InGaAs DHBTs with InGaAsP in the collector that has a highly Zn-doped base was investigated using various emitter-widths and lengths as functions of collector current I/sub C/ and collector/emitter voltage V/sub CE/. Narrowing the emitter-width is significantly more effective for increasing f/sub max/ than shortening the emitter-lengths. A DHBT with a narrow 0.8-/spl mu/m emitter-metal has an ultra-high f/sub max/ of 267 GHz and f/sub T/ of 144 GHz at an I/sub C/ as low as 4 mA. This increase in f/sub max/ is attributed to the low product of the base resistance and reduced base/collector capacitance.

Ultra-high f/sub max/ and f/sub T/ InP/InGaAs double-heterojunction bipolar transistors with step-graded InGaAsP collector

A heterojunction bipolar transistor includes a collector contact layer constituted by a high-concentration first semiconductor layer of a first conductivity type formed on a semiconductor substrate, a collector region stacked on the collector contact layer, a base layer constituted by a fifth semiconductor layer of a second conductivity type formed on the collector region, and an emitter layer constituted by a semiconductor layer of the first conductivity type formed on the base layer. The collector region is constituted by a second semiconductor layer, a third semiconductor layer of the second conductivity type having an impurity concentration higher than that of the second semiconductor layer, and a fourth semiconductor layer of the first conductivity type having a band gap energy higher than that of each of the first and second semiconductor layers and an impurity concentration higher than that of the second semiconductor layer, and the fourth semiconductor layer and lower than that of the first semiconductor layer, the third semiconductor layer, and the second semiconductor layer are sequentially formed on the collector contact layer in an order named.

Heterojunction bipolar transistor and integrated circuit device using the same

Type-II InP/GaAsSb/InP double heterojunction bipolar transistors (DHBTs) with a 15-nm base were fabricated by contact lithography: 0.73/spl times/11 /spl mu/m/sup 2/ emitter devices feature f/sub T/=384GHz (f/sub MAX/=262GHz) and BV/sub CEO/=6V. This is the highest f/sub T/ ever reported for InP/GaAsSb DHBTs, and an "all-technology" record f/sub T//spl times/BV/sub CEO/ product of 2304 GHz/spl middot/V. This result is credited to the favorable scaling of InP/GaAsSb/InP DHBT breakdown voltages (BV/sub CEO/) in thin collector structures.

15-nm base type-II InP/GaAsSb/InP DHBTs with F/sub T/=384 GHz and a 6-V BV/sub CEO/

InP/InGaAs double‐heterostructure bipolar transistors (DHBTs), incorporating a new collector structure featuring ‘‘pn pair doping’’ in the heterointerface vicinity, have been fabricated using a low‐pressure metalorganic chemical vapor deposition (MOCVD) method. These transistors provide high collector current densities over 1×105 A/cm2, indicating the successful suppression of current blocking. S‐parameter measurements determine the high current gain cutoff frequencies of 130 GHz. These values favorably compare with those of conventional InGaAs‐collector HBTs fabricated for comparison, suggesting that the InP collectors have excellent electron transport properties.

High-speed InP/InGaAs double-heterostructure bipolar transistors with suppressed collector current blocking

We report the successful growth of high‐quality InP/InGaAs double‐heterojunction bipolar transistors with heavily Zn‐doped base layers (p=4×1019 cm−3) using metalorganic vapor phase epitaxy. Interrupting the growth for 30 min after growing a heavily Si‐doped subcollector (n=2×1019 cm−3) is shown to eliminate the excessive nonequilibrium group III interstitials that enhance abnormal Zn diffusivity in the subsequently grown base region. Gummel plots of the fabricated microwave transistors show that they have ideal turn‐on characteristics in spite of having only 5‐nm‐thick undoped spacer layers inserted between the emitter and base. The transistors obtain a maximum oscillation frequency fmax of 178 GHz and a current gain cutoff frequency fT of 126 GHz.

H. Nakajima

Papers

High-speed InP/InGaAs double-heterostructure bipolar transistors with suppressed collector current blocking

High‐performance Zn‐doped‐base InP/InGaAs double‐heterojunction bipolar transistors grown by metalorganic vapor phase epitaxy