Double-heterojunction Bipolar Transistor Structures Research Articles

InGaAs/InP DHBT small‐signal model up to 325 GHz with two intrinsic base resistances

AbstractIn this paper, a novel small‐signal equivalent‐circuit model of terahertz InGaAs/InP double‐heterojunction bipolar transistor (DHBT) is presented. Two intrinsic base resistances are introduced to represent the nonuniform extrinsic impedance of base‐emitter and base‐collector junctions separately. This treatment makes the high‐frequency model more close to the triple‐mesa InP DHBT structure. Systematical parasitic parameter extraction method and intrinsic element initialization of a 0.5 μm * 5μm InGaAs/InP DHBT are presented. As a high‐frequency device model, inter‐electrode parasitic capacitances are calculated by three‐dimensional electromagnetic simulation. The proposed model results in a good agreement with measured multibiased S‐parameters up to 325 GHz.

A monolithic GaAs-based short wavelength smart pixel based on fabricated p–i–n PD, aDHBT and a VCSEL

For the first time a smart pixel that can function as a building block for an optical transceiverwith circular dimensions is fabricated using an InGaP/GaAs double heterojunction bipolartransistor (DHBT) and a GaAs/AlGaAs vertical cavity surface emitting laser (VCSEL). Anovel InGaP DHBT structure based on an abrupt base–collector heterojunction, theδ+-layer composite collector structure, is employed in this work. The DHBTshowed a breakdown voltage of 13 V and a cut-off frequency of 32 GHz atIc = 30 mA. Also a high performance 850 nm infrared VCSEL exhibited athreshold current of 3.5 mA with a maximum optical output of 4.8 mW atIc = 20 mA and forward voltage of 1.8 V. The detector, comprising the base-to-collectorjunction of the DHBT as a p–i–n photodiode (PD), produced a photocurrent of180 µA for a given input power of 0.3 mW.

Practical photoluminescence and photoreflectance spectroscopic system for optical characterization of semiconductor devices

We present a practical experimental design for performing photoluminescence (PL) and photoreflectance (PR) measurements of semiconductors with only one PL spectroscopic system. The measurement setup is more cost efficient than typical PL-plus-PR systems. The design of the experimental setup of the PL-PR system is described in detail. Measurements of two actual device structures, a high-electron-mobility transistor (HEMT) and a double heterojunction-bipolar transistor (DHBT), are carried out by using this design. The experimental PL and PR spectra of the HEMT device, as well as polarized-photoreflectance (PPR) spectra of the DHBT structure, are analyzed in detailed and discussed. The experimental analyses demonstrate the well-behaved performance of this PL-PR design.

Molecular beam epitaxial growth and characterization of InP/GaAsSb/InP double heterojunction bipolar transistors

InP/GaAsSb/InP double heterojunction bipolar transistor structures were grown in a solid-source molecular beam epitaxy system. Carbon or Be was used for the p-type doping of GaAs 0.51Sb 0.49. Hole concentrations in excess 2×10 20 cm −3 were obtained in carbon doped GaAs 0.51Sb 0.49 films. InP/GaAsSb/InP double heterojunction bipolar transistors were fabricated as wet-etched triple mesa structures. Common-emitter current gain, β, >80 was measured for large area devices with 20×20 μm 2 emitter geometry, and a base doping of 1×10 19 cm −3. BV CEO>6 V was measured for devices incorporating a 2000 Å thick InP collector. The gain of the transistor decreased to 20 as the base doping level was increased to 5×10 19 cm −3.

Theoretical investigation of an InGaP/GaAs heterostructure-emitter bipolar transistor with a wide-gap collector

We theoretically analyse the performance of an InGaP/GaAs heterostructure-emitter bipolar transistor (HEBT) with a wide-gap collector. Using an exact simulation, we report on detailed calculations and studies including majority-carrier and minority-carrier profiles, recombination-rate distributions, and dc and ac performances. By introducing an undoped GaAs spacer and a heavily doped transition layer into the conventional base–collector heterojunctions, the field across the inserted layers is high enough to pull down the potential spike drastically; thus the knee-shaped characteristics and reach-through effect are not observed. Moreover, the base–emitter (B–E) structure, which we have used, contains an effective p–n homojunction and a hetero-confinement layer to substantially reduce the potential spike at the B–E junctions. Therefore the studied device has exhibited a relatively smaller offset voltage and higher current gain than those of a conventional heterojunction bipolar transistor. The simulated results particularly reveal that a proposed HEBT with an appropriately designed device structure exhibits higher efficiency, lower offset voltage (≤30 mV), lower saturation voltage (≤0.5 V), uniform current gain (∼25), lower operated voltage, higher breakdown voltage and improved characteristics as compared to those obtained from a conventional double heterojunction bipolar transistor structure.

Evaluation of encapsulation and passivation of InGaAs/InP DHBT devices for long-term reliability

Device encapsulation and passivation are critical for long-term reliability and stability. Several encapsulation techniques were evaluated in terms of degradation of electrical characteristics, gap filling under the mesa structures, and adhesion to the semiconductor and metal surfaces. These included plasma enhanced chemical vapor deposited (PECVD) SiO2, electron cyclotron resonance CVD SiNx, spin-on glass, benzocyclobutene, and polyimide. Damage from plasma exposure caused gain degradation in the devices. Spin-on coatings cause little to no gain degradation, provided that there is minimal stress in the cured film. SOG and BCB films have acceptable adhesion properties and were excellent for gap filling. Polyimide films have excellent adhesion properties, however, they were poor at gap filling and had a great deal of shrinkage during curing. Device passivation was evaluated using double heterojunction bipolar transistor structures with either an abrupt or graded emitter-base junction. Abrupt junction devices had the self-aligned base metal directly on the p+ InGaAs base. Graded junction devices had the base metal on top of graded InGaAsP layers, which the metal was diffused through, to make contact to the base region. Abrupt junction devices stressed at an initial JE of 90 kA/cm2 at a VCE of 2V at 25°C degraded 20% within 70 h of operation, whereas, the graded junction devices show no degradation in dc characteristics after operation for over 500 h. Typical common emitter current gain was 50. An ft of 80 and fmax of 155 GHz were achieved for 2×4 µm2 emitter size devices.

GaInAs/InP DHBT incorporating thick extrinsic base and selectively regrown emitter

A novel approach for realising a double heterojunction bipolar transistor (DHBT) with a low base resistance, which incorporates a thick extrinsic base and a regrown emitter, is proposed and demonstrated. A combination of selective MOVPE regrowth and selective wet chemical etching resulted in a new self-aligned DHBT structure. Fabricated microwave transistors exhibited good DC and microwave characteristics.

The use of organometallic group-V sources for the metalorganic molecular beam epitaxy growth of In 0.48Ga 0.52P/GaAs and In 0.53Ga 0.47As/InP heterojunction bipolar device structures

This paper describes the use of tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) as replacements for arsine and phosphine in MOMBE/CBE for the production of device structures with state-of-the-art performance. The growth system used for this work is based on the use of elemental group-III and dopant sources, and employs thermal crackers for the low pressure precracking of TBA and TBP. Device structures fabricated in the In 0.48Ga 0.52P/GaAs materials system include single- and double-heterojunction bipolar transistors (SHBTs and DHBTs). Current gains as high as 2690 have been obtained with these transistors. Deep level transient spectroscopy (DLTS) measurements of the emitter-base junctions of these transistors reveals the absence of deep level traps, in contrast to similar devices fabricated using AlGaAs/GaAs. Device structures fabricated in the In 0.53Ga 0.47As/InP materials system include SHBTs, DHBTs, and resonant tunneling bipolar transistors (RTBTs). In 0.53Ga 0.47As/InP SHBTs with record maximum oscillation frequencies (ƒ max) of > 180 GHz have been produced with high breakdown voltages BV CEO and BV CBO of 8.1 and 17 V, respectively. In addition, DHBTs with ƒ T=134 GHz and ƒ max=137 GHz have been fabricated. Resonant tunneling bipolar transistors, consisting of a structured AlAs/In x Ga 1− x As resonant tunneling double barrier vertically integrated into the emitter of an InP/InGaAs double heterojunction bipolar transistor structure, have been demonstrated. These transistors have room temperature peak-to-valley current ratio of approximately 20, current gain of 100, and breakdown voltage exceeding 5 V, allowing the demonstration of the first room temperature resonant tunneling transistor integrated circuits.

Influence of launching energy on collector transport in InP/InGaAs double-heterojunction bipolar transistors

Summary form only given. The authors report the drastic change of electron velocity in InP/InGaAs DHBT (double-heterojunction bipolar transistor) collectors, depending on the collector potential profile. By increasing the electron injection energy into the InP collector, electron transport in the satellite valleys becomes significant, leading to velocity reduction from 3.5*10/sup 7/ cm/s to 1.6*10/sup 7/ cm/s. Gamma -valley-dominated transport is at least more than twice as fast as upper-valley-dominated transport. Consequently, nonequilibrium transport in the InP collector plays an essential role in determining the high-speed performance of InP/InGaAs DHBTs. This experiment used DHBT structures grown by MOCVD (metal-organic chemical vapor deposition). >

Double-heterojunction bipolar transistors in InP/GaInAs grown by metal organic chemical vapour deposition

Double-heterojunction bipolar transistor structures in InP/GaInAs have been grown by low-pressure metal organic chemical vapour deposition. Good control of the Zn dopant in the GaInAs base layer was achieved, and devices with current gains up to 300 at current densities of 1.4kA/cm2 have been demonstrated.