Pnp Heterojunction Bipolar Transistor Research Articles

AlGaAs/GaAs/InGaAs pnp-type vertical-cavity surface-emitting transistor-lasers.

We report on the design, fabrication and analysis of vertical-cavity surface-emitting transistor-lasers (T-VCSELs) based on the homogeneous integration of an InGaAs/GaAs VCSEL and an AlGaAs/GaAs pnp-heterojunction bipolar transistor (HBT). Epitaxial regrowth confinement, modulation doping, intracavity contacting and non-conducting mirrors are used to ensure a low-loss structure, and a variety of design variations are investigated for a proper internal biasing and current injection to ensure a wide operating range. Optimized devices show mW-range output power, mA-range base threshold current and high-temperature operation to at least 60°C with the transistor in its active mode of operation for base currents well beyond threshold. Current confinement schemes based on pnp-blocking layers or a buried tunnel junction are investigated as well as asymmetric current injection for reduced extrinsic resistances.

Effects of carbon on phosphorus diffusion in SiGe:C and the implications on phosphorus diffusion mechanisms

The use of carbon (C) in SiGe base layers is an important approach to control the base layer dopant phosphorus (P) diffusion and thus enhance PNP heterojunction bipolar transistor (HBT) performance. This work quantitatively investigated the carbon impacts on P diffusion in Si0.82Ge0.18:C and Si:C under rapid thermal anneal conditions. The carbon molar fraction is up to 0.32%. The results showed that the carbon retardation effect on P diffusion is less effective for Si0.82Ge0.18:C than for Si:C. In Si0.82Ge0.18:C, there is an optimum carbon content at around 0.05% to 0.1%, beyond which more carbon incorporation does not retard P diffusion any more. This behavior is different from the P diffusion behavior in Si:C and the B in Si:C and low Ge SiGe:C, which can be explained by the decreased interstitial-mediated diffusion fraction fIP, SiGe to 95% as Ge content increases to 18%. Empirical models were established to calculate the time-averaged point defect concentrations and effective diffusivities as a function of carbon and was shown to agree with previous studies on boron, phosphorus, arsenic and antimony diffusion with carbon.

Impact of Ge-Profile in Base on SiGe pnp HBT’s Performance

SiGe heterojunction structure much improves the performance of PnP HBT (heterojunction bipolar transistor), which focus on the impact of Ge component distribution in the base on the current gain and characteristic frequency . The triangular distribution in the base, including zero-doping and non-zero-doping at the starting point, will form a Ge-gradient acceleration filed for the minority carriers in the base to reduce the base transport time and increase current density and working frequency. Extend Ge to the collector region to eliminate the effect of the valence band spike barrier at the collector junction, further improving the performance of the pnp HBT. By the simulations and optimizations in this paper, the and of pnp SiGe HBT improves evidently, and the results can be referenced in the design of SiGe devices and circuits.

InGaP/GaAs pnp Heterojunction Bipolar Transistor with δ-Doped Sheet between Base-Emitter Junction

In this article, a novel InGaP/GaAs pnp δ-doped heterojunction bipolar transistor is first demonstrated. Though the valence band discontinuity at InGaP/GaAs heterojunction is relatively large, the addition of a δ-doped sheet between two spacer layers at the emitter-base junction effectively eliminates the potential spike and increases the confined barrier for electrons, simultaneously. Experimentally, a high current gain of 25 and an offset voltage of 100 mV are achieved. The offset voltage is much smaller than the conventional InGaP/GaAs pnp HBT. The proposed device could be used for linear amplifiers and low-power complementary integrated circuit applications.

2D device-level simulation study of strained-Si pnp heterojunction bipolar transistors on virtual substrates

A novel strained-Si pnp heterojunction bipolar transistor (HBT) design, suitable for virtual substrate technology, is proposed that is inherently free from the detrimental valence band barrier effects usually encountered in conventional SiGe pnp HBTs on silicon. It takes advantage of the heterojunction formed between a strained-Si layer and a relaxed SiGe buffer (virtual substrate), whose associated valence band offset appears favorable for minority hole transport at the base/collector junction. From two-dimensional (2D) numerical simulation, it is found that the newly proposed strained-Si pnp HBT substantially outperforms the equivalent BJT on a silicon substrate in terms of DC and high-frequency characteristics. A threefold increase in maximum current gain β, a fourfold improvement in peak f t and a 2.5 times increase in peak f max are predicted for strained-Si pnp HBTs on a 50% Ge virtual substrate in comparison with identical conventional silicon pnp BJTs.

Technology and First Electrical Characteristics of Complementary NPN and PNP InAlAs/InGaAs Heterojunction Bipolar Transistors

A selective molecular beam epitaxy (MBE) regrowth approach is presented and applied in the demonstration of complementary InP heterojunction bipolar transistor (HBT) technology for monolithic integration of NPN and PNP HBTs. State-of-art performance has been observed: The DC gain was 35 for both integrated NPN and PNP HBTs. fT of 79.6 GHz and fmax of 109 GHz were achieved for NPN devices while fT of 11.6 GHz and fmax of 22.6 GHz were achieved for PNP devices. Little performance degradation has been observed compared with same design NPN or PNP HBT layers grown on individual substrates. Monolithic microwave integrated circuits (MMICs) based on complementary InP HBT technology have been studied for the first time using this technology and their electrical characteristics are presented.

DC and High Frequency Characterization of Metalorganic Chemical Vapor Deposition (MOCVD) Grown InP/InGaAs PNP Heterojunction Bipolar Transistor

InP/InGaAs PNP heterojunction bipolar transistor (HBT) layers have been grown by metalorganic chemical vapor deposition (MOCVD) and devices have been fabricated using a self-aligned processing technology. A zinc-doped InP layer has been employed as the wide-bandgap emitter layer for the PNP HBT. The base layer used a 500 Å thick n-type InGaAs layer doped at 5×1018 cm-3. Successful high frequency operation of these devices has been demonstrated. A single-emitter 1×20 µm2 MOCVD-grown PNP InP/InGaAs HBT achieved current gain cutoff frequency (fT) of more than 11 GHz at a current density (JC) of 8.25×104 A/cm2.

A Gummel–Poon model for pnp heterojunction bipolar transistors with a compositionally graded base

A modified Gummel–Poon model has been developed for the pnp heterojunction bipolar transistor which matches thermionic emission–diffusion of holes across the emitter–base heterojunction with drift–diffusion transport across a graded base. The effects of a high current density on base pushout and the collector junction capacitance have been incorporated to describe the falloff in current gain and high frequency performance. The model's predictions have been compared with reported device measurements and results from a commercial, numerical device simulator for an InP-based device with good agreement found. The model provides an improved description of device performance that will be of use to device designers.

Emitter-base bias dependence of the collector current ideality factor in abrupt Pnp AlGaAs/GaAs heterojunction bipolar transistors

Starting with the 4×4 Luttinger–Kohn Hamiltonian and making use of the axial approximation, we calculate the emitter current as a function of the applied forward emitter-base bias for a typical Pnp AlGaAs/GaAs single heterojunction bipolar transistor (HBT). While including the effects of emitter series resistance and recombination in the quasi-neutral base and emitter-base space-charge region, we then calculate the collector current density versus emitter to base bias and find it to be in excellent agreement with the experimental results for a Al0.4Ga0.6As/GaAs Pnp HBT recently reported in the literature. For that structure, the collector current ideality factor is found to increase from 1.1 at low forward bias VEB to 3.0 at large applied emitter-base forward bias approaching the built-in potential. Experimental values are equal to 1.2 and 2.25 at low and large VEB, respectively.

AlGaAs/GaAs Pnp HBT with 54 GHz f/sub max/ and application to high-performance complementary technology

Summary form only given. A self-aligned AlGaAs/GaAs Pnp HBT (heterojunction bipolar transistor) with a maximum frequency of oscillation of 54 GHz is reported. Improvements in device speed over previous work were obtained by optimization of epitaxial structure and reduction of base contact resistance. The PnP epitaxial structure was grown by nonarsine MOVPE (metal-organic vapor-phase epitaxy), with silicon and carbon as the donor and acceptor dopants. The Pnp HBT epitaxial structure was incorporated into recessed areas in wafers with a previously grown Npn HBT epi structure, and the two device types were fabricated simultaneously. Pnp and Npn devices on a single wafer achieved f/sub max/ of 50 and 90 GHz, respectively. >

High-performance microwave AlGaAs-InGaAs Pnp HBT with high-DC current gain

An Pnp heterojunction bipolar transistor (HBT) which had among the highest reported values of f/sub T/( approximately 23 GHz) and f/sub max/( approximately 40 GHz) employed a heavily doped InGaAs pseudomorphic base. However, this HBT had very low values of DC current gain (<or=4). Pnp microwave HBTs with a modified base design are reported. These HBTs not only achieve similar high-frequency performance, but also attain dramatically higher current gain values approximately 90.<<ETX>>

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.