Self-aligned InAlAs/InGaAs heterojunction bipolar transistor with aburied subcollector grown by selective epitaxy

We report the first microwave characterization of an In_0.52 Al_0.48As/In_0.53Ga_0.47As heterojunction bipolar transistor (HBT) with a buried InGaAs subcollector grown by selective epitaxy. The study compares two HBT's having identical 2×10 μm² self-aligned emitter fingers but different subcollectors. Improvement in microwave performance of the selectively-grown HBT over the conventional HBT was observed due to the reduced parasitic base-collector capacitance achieved by incorporating the selectively-grown buried subcollector     

Modeling of SiGe-base heterojunction bipolar transistor with gaussian doping distribution

The results of numerical modeling of the base transit time and collector current of SiGe-base heterojunction bipolar transistors with a Gaussian base doping profile and two Ge profiles (linearly graded and box) are presented for the first time. The importance of including the dependence of minority carrier mobility on the drift field and the dependence of the effective density of states on the Ge concentration along the base is demonstrated through the analysis of base transit time and collector current. A function describing the decrease of the density of states product in strained SiGe layers with increasing Ge concentration is proposed.     

An amorphous SiC:H emitter heterojunction bipolar transistor

After confirming the successful application of the amorphous SiC:H(a-SiC:H)/crystalline Si(c-Si) heterostructure in a solar cell and considering its prospective application in Bi-CMOS devices, an attempt has been made to apply the same in the fabrication of a heterojunction bipolar transistor. A p-n-p heterojunction bipolar transistor with a wide band-gap boron-doped amorphous SiC:H emitter and crystalline Si (base, collector) has been realized and is reported here for the first time. Good device performance has been observed at the a-SiC:H deposition temperature of 450°C. Preliminary results gave a current gain,h_{FE(max)}) of 50 at a current density of approximately 2.4 A/cm²(base dose 2 × 10¹²/cm², width ≃ 0.4 µm). Temperature dependence of the transistorh_{FE}-I_{C}characteristics was also studied.     

AlGaAs/GaAs pnp heterojunction bipolar transistor with carbon-doped collector and emitter grown by atomic layer epitaxy

The first AlGaAs/GaAs pnp heterojunction bipolar transistor (HBT) grown entirely by atomic layer epitaxy (ALE) is reported. Carbon was used as the p-type dopant in the emitter and collector. The use of carbon, with its low diffusivity and the potential for very heavy doping, will lead to reduced emitter and collector resistances in a pnp structure. For the devices reported here, a common emitter current gain over 100 was obtained, with good I/V characteristics.<>     

Atomic layer epitaxy grown heterojunction bipolar transistor havinga carbon-doped base

The fabrication of a GaAs/AlGaAs heterojunction bipolar transistor (HBT) having a carbon-doped base is reported. The low diffusion coefficient of carbon makes it attractive for HBT applications since it will prevent out diffusion. The base was grown by atomic layer epitaxy (ALE), from a TMG (trimethylgallium) source that allowed the incorporation of carbon into the layer from the partially related TMG metal carbide. HBTs with common-emitter current gains of 100 were obtained at current densities of 1300 A-cm^-2     

A heterojunction bipolar transistor with a thin α-Si emitter

In this paper, a modified silicon heterojunction bipolar transistor is proposed and demonstrated. The structure uses a very thin n⁺ amorphous silicon layer as the emitter to enhance the emitter injection efficiency and reduce the emitter resistance as well as improve the frequency response of the device     

Self-aligned AlInAs-GaInAs heterojunction bipolar transistors andcircuits

AlInAs-GaInAs heterojunction bipolar transistors (HBTs) and static flip-flop frequency dividers have been fabricated. An f_t and an f_max of 49 and 62 GHz, respectively, have been achieved in a device with a 2×5-μm² emitter. Current-mode logic (CML) was used to implement static divide-by-two and divide-by-four circuits. The divide-by-two circuit operated at 15 GHz with 82-mW power dissipation for the single flip-flop. The divide-by-four circuit operated at 14.5 GHz with a total chip power dissipation of 444 mW     

Base transit time for SiGe-base heterojunction bipolar transistors

The base transit time expressions for SiGe base heterojunction bipolar transistors are presented including the accelerating field effects due to the base bandgap grading and doping grading, and the retarding field (opposing drift field) effect from the graded boron profile down towards the emitter. It is found that the retarding field exhibits 40-80% contribution to the base transit time, depending on the boron concentration near the emitter. The results of base transit time from these analytic expressions are unambiguously supported by the published simulation data.<>     

InGaAs/lnP heterojunction bipolar transistor grown by all-solidsource molecular beam epitaxy

State-of-the-art InGaAs/InP heterojunction bipolar transistors were grown by all-solid source molecular beam epitaxy. Fabricated transistors showed cutoff frequencies of >100 GHz with an emitter area of 1.5×5 μm². Together with recent studies. These results demonstrate that the valved cracker technique is a very competitive nontoxic growth method     

A tunneling emitter bipolar transistor

We propose a new device-a Tunneling Emitter Bipolar Transistor (TEBT)-where the enhancement of the emitter injection efficiency is achieved by utilizing a very large difference in the tunneling probabilities for electrons and holes in a thin doped graded AlGaAs layer. This layer is inserted between the n-type GaAs emitter and p-type GaAs base. This device should have a high emitter efficiency and low parasitic resistances.     

GaAs-GaAsSb based heterojunction bipolar transistor

The fabrication of the first GaAs-GaAsSb based heterojunction bipolar transistor is reported. Maximum current gains of 25 at a base current of 1 mA have been measured on devices employing a p-type 1000 AA GaAs/sub 0.93/Sb/sub 0.07/ base doped at 1*10/sup 19/ cm/sup -3/ and GaAs emitter and collector regions with graded heterointerfaces. At present, devices so fabricated show unstable behaviour.<>     

Si/SiGe heterojunction bipolar transistor with base doping highly exceeding emitter doping concentration

A Si/Si/sub 0.8/Ge/sub 0.2/ heterojunction bipolar transistor was fabricated having emitter, base and collector contacts at the wafer surface. The base doping concentration amounted to 10/sup 19//cm/sup 3/ which was 20 times the emitter concentration. Due to the pronounced difference in bandgap energy a current gain of 17 was reached.<>     

Analyses of delta-doped emitter bipolar transistor

In this article, the theoretical model of delta-doped emitter bipolar transistor that included the effect of bandgap shrinkage is presented. The recombination in emitter set-back layer is also considered. We also present the calculated results for the current gain as a function of barrier height, barrier width, and emitter set-back layer thickness. The experimental results of the device are also given.     

A high-gain GaAs/AlGaAs n-p-n heterojunction bipolar transistor on(100) Si grown by molecular beam epitaxy

High-gain GaAs/AlGaAs n-p-n heterojunction bipolar transistors (HBT's) on Si substrates grown by molecular beam epitaxy (MBE) have been fabricated and tested. In this structure, an n⁺-InAs emitter cap layer was grown in order to achieve a nonalloyed ohmic contact. Typical devices with an emitter dimension of 50×50 μm² exhibited a current gain as high as 45 at a collector current density of 2×10³ A/cm² with an ideality factor of 1.4. This is the highest current gain reported for HBT's grown on Si substrates. Breakdown voltages as high as 10 and 15 V were observed for the emitter-base and collector-base junctions respectively. The investigation on devices with varying emitter dimensions demonstrates that much higher current gains can be expected     

Heavily doped base GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy

The first demonstration of a GaInP/GaAs heterojunction bipolar transistor grown by chemical beam epitaxy is reported. A common-emitter current gain of 30 at a current density of 110 A/cm/sup 2/ is obtained for a beryllium base doping as high as 8*10/sup 19/ cm/sup -3/. The base sheet resistance of 140 Omega / Square Operator is among the lowest reported values.<>     

A fully planar heterojunction bipolar transistor

A fully planar heterojunction bipolar transistor (HBT) in the normal emitter-up configuration is reported. The process utilizes a two-step epitaxial deposition with an intervening selective ion implant of bases. A process is described, the aluminum lift-off (ALL) process, with which refractory metal contacts have been used. Large test devices fabricated have dc gains of β = 600.     

DC characterization of an InP-InGaAs tunneling emitter bipolar transistor (TEBT)

The dc performances of a novel InP-InGaAs tunneling emitter bipolar transistor (TEBT) are studied and demonstrated. The studied device can be operated under an extremely wide collector current regime larger than 11 decades in magnitude (10/sup -12/ to 10/sup -1/ A). A current gain of 3 is obtained even operated at an ultralow collector current of 3.9/spl times/10/sup -12/ A (1.56 /spl times/10/sup -7/ A/cm/sup 2/). The common-emitter and common-base breakdown voltages of the studied device are higher than 2 and 5 V, respectively. Furthermore, a very low collector-emitter offset voltage of 40 mV is found. The temperature-dependent dc characteristics of the TEBT are measured and studied. Consequentially, based on experimental results, the studied device provides the promise for low-power electronics applications.     

AlGaN/GaN heterojunction bipolar transistor

We demonstrate the first GaN bipolar transistor. An AlGaN/GaN HBT structure was grown by MOCVD on c-plane sapphire substrate. The emitter was grown with an Al_0.1Ga_0.9N barrier to increase the emitter injection efficiency. Cl₂ RIE was used to pattern the emitter mesa, and selectively regrown base contact pads were implemented to reduce a contact barrier associated with RIE etch damage to the base surface. The current gain of the devices was measured to be as high as three with a base width of 200 nm. DC transistor characteristics were measured to 30 V V_CE in the common emitter configuration, with an offset voltage of 5 V. A gummel plot and base contact characteristics are also presented     

HBT结构的新进展

介绍了以In0.03Ga0.97As0.99N0.01材料为基区的GaAs异质结双极型晶体管和以GaAs0.51Sb0.49材料为基区的InP HBT.讨论了GaAs和InP HBT结构的新进展及其对性能的改善,并对各结构的适用范围和优缺点进行了比较.     

A novel technology to form self-aligned emitter ledge for heterojunction bipolar transistors

We have proposed and successfully demonstrated a novel and simple process to fabricate self-aligned emitter passivation ledges for heterojunction bipolar transistors (HBTs) without using additional dielectric etch masks or dual etch-stop layers in the emitter. In this new ledge formation process, the emitter ledges are fabricated by the formation of photoresist sidewall spacers followed by a wet-chemical etch process. The effectiveness of this new ledge formation technology has been confirmed in AlGaAs/GaAs HBTs. Since the proposed ledge technology is very simple and without using any etch-stop layers (thus independent of material systems), it appears to be very promising for HBT fabrication.