Sheng-Yu Wang

InGaAsSb/InP Double Heterojunction Bipolar Transistors Grown by Solid-Source Molecular Beam Epitaxy

This letter investigates the dc characteristics of a double heterojunction bipolar transistor (DHBT) with a compressively strained InGaAsSb base, which is grown by solid-source molecular beam epitaxy. The novel InP/InGaAsSb HBT has a lower base/emitter (B/E) junction turn-on voltage, a lower offset voltage, and a junction ideality factor closer to unity than the conventional InP/InGaAs composite collector DHBT. These characteristics are attributed to the transistors type-I B/E junction and type-II base/collector junction, which facilitates carrier transport for low power, high current density, and high-speed operation. Heterojunction bipolar transistors (HBTs), InP/InGaAsSb, molecular beam epitaxy (MBE).

Metallic wafer and chip bonding for LED packaging

LED chip bonding on Cu foil have been investigated. We found that with thicker Cu coating on the back side of LED chip, a better lighting efficiency will be obtained. Indium(In) chip bonding shows slightly better thermal dissipation than Sn chip bonding. Also, a new wafer bonding for producing GaN on Si substrate have been successfully demonstrated. This technique enables us to produce a high temperature bonding by using a low temperature process.

Low Surface Recombination in InAlAs/InGaAsSb/InGaAs Double Heterojunction Bipolar Transistors

The surface recombination behavior of a series of InAlAs/InGaAsSb/InGaAs heterojunction bipolar transistors (HBTs) is investigated. It is found that the InGaAsSb base HBTs have lower emitter periphery surface recombination current density (KSURF) than the HBT with an InGaAs base. It is attributed to the type-I band lineup at the B-E junction and the surface pining of the antimonide base layer. A lower S0 is deduced for the DHBT with a higher Sb content in the InGaAsSb base.

DC Characteristics of InAlAs/InGaAsSb/InGaAs Double Heterojunction Bipolar Transistors

DC electrical characteristics of a series of InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistors (DHBTs) that are grown on InP by molecular beam epitaxy are reported and analyzed. The InGaAsSb base of the transistors leads to a type-I base-emitter junction and a type-II base-collector junction, resulting in unique device characteristics, such as low turn-on voltage, low crossover current, and constant current gain over a wide current range. In addition, the DHBTs exhibit rather high current gains despite the use of a heavily doped thick InGaAsSb base layer. This indicates the long minority carrier lifetime of the InGaAsSb material. A high current gain over base sheet resistance ratio is, thus, realized with these novel DHBTs.

High Current and Low Turn-On Voltage InAlAs/InGaAsSb/InGaAs Heterojunction Bipolar Transistor

This study investigates the DC characteristics of a heterojunction bipolar transistor (HBT) with a quaternary InGaAsSb base, grown by solid-source molecular beam epitaxy (MBE). The novel In_0.52Al_0.48As/In_xGa_1-xAs_1-ySb_y HBT has a lower base/emitter (B/E) junction turn-on voltage, a lower V_CE.offset voltage and a greater junction ideality factor than conventional In_0.52Al_0.48As/In_0.53Ga_0.47As single HBT structures. The quaternary In_xGa_1-xAs_1-ySb_y base provides a type-I B/E junction and a type-II base/collector (B/C) junction, suggesting that the InGaAsSb base HBT has great potential for low-power and high-speed applications.

Characterization of InAlAs/In 0.25 Ga 0.75 As 0.72 Sb 0.28 /InGaAs double heterojunction bipolar transistors

We report on the characterization of InP-based heterojunction bipolar transistors (HBTs) with low turn-on voltage and high current gain by using InGaAsSb as the base layer. The low turn-on voltage of 0.43 V is attributed to the smaller band gap of the In<inf>0.25</inf>Ga<inf>0.75</inf>As<inf>072</inf>Sb<inf>0.28</inf> material. High current gain of 74 is observed despite a heavily Be-doped (9.0×10¹⁹ cm⁻³) base is used, suggesting a long minority carrier lifetime (τ<inf>n</inf>) in the InGaAsSb material. Moreover, low specific contact resistivity of 5×10⁻⁸ Ω-cm² is also demonstrated on separate In<inf>0.25</inf>Ga<inf>0.75</inf>As<inf>072</inf>Sb<inf>0.28</inf> samples.

InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistors with high current gain and low base sheet resistance

The proposed InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistors (DHBTs) exhibit a rather high current gain despite the use of a highly doped and thick InGaAsSb base layer, indicating that a high minority carrier lifetime exists in the InGaAsSb material. A high current gain over sheet resistance ratio, low cross-over current and a wide constant current gain range have been achieved, suggesting that the novel InAlAs/InGaAsSb/InGaAs DHBTs are grown with a high quality InGaAsSb base layer.

Ultra low turn-on voltage and high-current InP DHBT with a pseudomorphic In 0.37 Ga 0.63 As 0.89 Sb 0.11 base

We report on the dc and microwave characteristics of an InP/InGaAsSb/InGaAs double heterojunction bipolar transistor grown by solid-source molecular beam epitaxy. The pseudomorphic In_0.37Ga_0.63As_0.89Sb_0.11 base reduces the conduction band offset (DeltaE_C) at the emitter/base (E/B) junction and the base band gap, which leads to a very low VBE turn-on voltage of 0.35 V at 1 A/cm². Current gain of 125 and peak f_T of 238 GHz have been obtained on the devices with an emitter size of 1times10 mum², suggesting that high current capability is achieved due to its type-II lineup at the InGaAsSb/InGaAs base/collector (B/C) junction.

DC Characteristics of GaAsSb/InGaAs Type-II Heterojunction Bipolar Transistor

InGaAs/InP single heterojunction bipolar transistor (SHBT) is the fastest HBT owing to its high current density and high electron saturation velocity. This work proposes a new structure with a GaAsSb/InGaAs B-C junction to improve upon the conventional SHBT. GaAsSb base material is used to maximize the conduction and valence band discontinuity in the lattice match material system.

InGaAs/InP heterojunction bipolar transistors with low offset voltage and current blocking

InGaAs/InP double heterojunction bipolar transistor with low offset voltage and low collector current blocking effect have been obtained using a combination of InGaAs spacers at the BE and BC junctions, and a highly doped n-type InP layer in the collector region. It is found that increasing the doping concentration of the n/sup +/-InP layer is more effective in lowering current blocking effect than increasing the InGaAs BC spacer thickness. Increasing base doping concentration is shown to be effective as well.