1/f noise characteristics of AlGaAs/GaAs heterojunction bipolartransistor with a noise corner frequency below 1 kHz

To reduce the low-frequency noise, HBTs with a large emitter size of 120×120 μm² are fabricated on abrupt emitter-base junction materials without undoped spacer. The HBTs exhibit an internal noise corner frequency of 100 Hz, which is much lower than about 100 kHz of conventional AlGaAs/GaAs HBTs. From the very low noise HBTs, the existence of resistance fluctuation 1/f noise is clearly verified by the simple comparison of collector current noise spectra with different base terminations. It is found that, at a high emitter-base forward bias, the resistance fluctuation 1/f noise becomes dominant for shorted base-emitter termination, but the internal 1/f noise dominant for open base. Device design rules for low noise small-feature size HBT, including resistance fluctuation, are discussed     

Microwave pnp AlGaAs/GaAs heterojunction bipolartransistor

The microwave performance of a pnp AlGaAs/GaAs heterojunction bipolar transistor was demonstrated for the first time. Common emitter current gains of 60 were obtained using MOCVD grown structures with 100 nm thick base layers and self-aligned emitter-base contacts. f_t and f_max values were 12 and 20 GHz respectively. Under common-base configuration, 8 dB gain was obtained at 10 GHz. Device performance was characterised under CW and pulsed conditions     

Regenerative switching characteristics of a novel electrical oroptical base-controlled AlGaAs/GaAs quantum-well heterojunction bipolartransistor

A report is presented on the regenerative switching characteristics of a novel AlGaAs/GaAs quantum-well heterojunction bipolar transistor (QWHBT) with an electrically or optically controlled base grown by molecular beam epitaxy (MBE). This double-barrier QWHBT exhibits excellent electrical switching characteristics of 7 V and 0.03 A/cm² at the switching condition and 4.5 V and 3.2 A/cm² at the holding condition. When the device is operating as an optical switch, the optical base-controlled sensitivity is 6×10 ^-3 V/μW. The effects of temperature on the device performance were evaluated at 77 and 300 K. The results show that it may be used as an all-optical switch (flip-flop) for optical parallel image processing     

Direct extraction of the AlGaAs/GaAs heterojunction bipolartransistor small-signal equivalent circuit

The authors describe a novel, direct technique for determining the small-signal equivalent circuit of a heterojunction bipolar transistor (HBT). The parasitic elements are largely determined from measurements of test structures, reducing the number of elements determined from measurements of the transistor. The intrinsic circuit elements are evaluated from y-parameter data, which are DC-embedded from the known parasitics. The equivalent-circuit elements are uniquely determined at any frequency. The validity of this technique is confirmed by showing the frequency independence of the extracted circuit elements. The equivalent circuit models the HBT s-parameters over a wide range of collector currents. Throughout the entire 1-18-GHz frequency range, the computed s-parameters agree very well with the experimental data     

Submicrometer self-aligned AlGaAs/GaAs heterojunction bipolartransistor process suitable for digital applications

A self-aligned process is developed to obtain submicrometer high-performance AlGaAs/GaAs heterojunction bipolar transistors (HBTs) which can maintain a high current gain for emitter sizes on the order of 1 μm². The major features of the process are incorporation of an AlGaAs surface passivation structure around the entire emitter-base junction periphery to reduce surface recombination and reliable removal of base metal (Ti/W) deposits from the sidewall by electron cyclotron resonance (ECR) plasma deposition of oxide and ECR plasma etching by NF₃. A DC current gain of more than 30 can be obtained for HBTs with an emitter-base junction area of 0.5×2 μm² at submilliampere collector currents. The maximum f_T and f_max obtained from a 0.5×2 μm² emitter HBT are 46 and 42 GHz, respectively at I_C=1.5 and more than 20 GHz even at I_C=0.1 mA     

A planar-doped 2D-hole gas base AlGaAs/GaAs heterojunction bipolartransistor grown by molecular beam epitaxy

A novel type of AlGaAs/GaAs heterojunction bipolar transistor (HBT) which uses a two-dimensional (2-D) hole gas base formed by planar doping using molecular-beam epitaxy (MBE) has been demonstrated. The base consists of a submonolayer of Be atoms of sheet concentration 0.5-5×10¹³ cm^-2 which is deposited during growth interruption by MBE. The transistor structure exhibits DC current gains up to 700. The effective base transit time is negligible in these transistors and it is postulated that very high-speed nonequilibrium transport may occur in the collector region     

High-frequency characteristics of AlGaAs/GaAs heterojunction bipolar transistors

The fabrication and high-frequency performance of MBE-grown AlGaAs/GaAs heterojunction bipolar transistors (HBT's) is described. The achieved gain-bandwidth product fTis 25 GHz for a collector current density Jcof 1 × 10⁴A/cm²and a collector-emitter voltage VCEof 3 V.fTcontinues to increase with the collector current in the high current density region over 1 × 10⁴A/cm²with no emitter crowding effect nor Kirk effect. The limitation on fTin fabricated devices is found to be caused mainly by the emitter series resistance.     

High-frequency output characteristics of AlGaAs/GaAs heterojunction bipolar transistors

A model has been developed which generates the high-frequency i/sub c/-v/sub ce/ output characteristics of bipolar transistors from computed cutoff frequency against current density data. The presented results, which can be used directly for large-signal modelling are the first report of high-frequency output characteristics of bipolar transistors.<>     

High linearity power X-band GaInP/GaAs heterojunction bipolartransistor

We report for the first time two-tone test results measured on a GaInP/GaAs HBT. A 2×400 μm² device delivered more than 1.3 W under one-tone testing at 7.5 GHz and output more than 1 W under two-tone. The corresponding intermodulation product is -14 dBc, and decreases to -21 and -36 dBc, respectively, at 3-dB and 10-dB back-off from the saturated two-tone output. These results demonstrate that GaInP/GaAs HBT's are suitable for microwave transmitter applications     

Modification of transconductance characteristics for ion-implanted GaAs/AlGaAs heterojunction MESFETs

Inverted GaAs/AlGaAs heterostructures grown by MOCVD have been used to fabricate conventional ion-implanted MESFETs. Two types of GaAs/AlGaAs heterojunctions are studied. One type has a compositionally graded AlGaAs layer which provides a built-in field and corresponding quantum well at the heterointerface. The other type has a constant-composition AlGaAs layer. 0.5 mu m gate devices fabricated using the ungraded AlGaAs layer show a maximum extrinsic transconductance G/sub m/ of 280 mS/mm and a small G/sub m/ variation over a gate voltage range of 1.5 V. In comparison, devices fabricated using the graded AlGaAs layer exhibit higher transconductance over all the gate voltages and an enhancement of G/sub m/ up to 420 mS/mm at low gate bias.<>     

Excess noise in AlGaAs/GaAs heterojunction bipolar transistors andassociated TLM test structures

Noise measurements both on transmission line model (TLM) test structures and on associated HBT's are presented. Contact noise is proved to be negligible in the TLM's related to the base structure of transistors. A Hooge parameter for p⁺⁺ doped GaAs is extracted. Activation energies are calculated from results versus temperature. Considering the TLM related to the structure of the emitter, it is shown that the g-r levels observed originate from the AlGaAs layer. Noise measurements on HBT's also exhibit excess noise. A value of the cutoff frequency between the equivalent input current white noise and the 1/f component is given. The base current dependencies associated with different measurement configurations suggest the 1/f noise to come from the base or the emitter-base junction. The g-r components are studied as a function of temperature. Activation energies are deduced. Finally a comparison of the TLM and HBT noise results is presented. The presence of the complex DX center and of g-r levels in the base region are proposed as possible origins for the g-r noise in HBT's     

1.5-W CW S-band GaInP/GaAs/GaInP double heterojunction bipolartransistor

We report the first large-signal power result from a double heterojunction bipolar transistor (DHBT) based on the GaInP/GaAs/GaInP material system. A CW output power of 1.51 W and a power added efficiency of 52% were achieved at 3 GHz. Because the GaInP collector has a relatively high bandgap of 1.89 eV, high DC bias voltage operation with collector bias extending to 20 V (for a 40-V swing) is possible in this GaInP/GaAs/GaInP DHBT. This high DC bias voltage operation represents a unique advantage over the more conventional AlGaAs/GaAs HBT     

Experimental comparison of base recombination currents in abrupt and graded AlGaAs/GaAs heterojunction bipolar transistors

The relative importance of the base bulk recombination current and the base-emitter junction space charge recombination current is examined for AlGaAs/GaAs HBTs with different grading schemes in the base-emitter junction. Experimental results demonstrate that, in abrupt HBTs, the base bulk recombination current is larger, and the base current increases with the base-emitter bias with an ideality factor of approximately 1. In contrast, in graded HBTs, the space charge recombination current dominates and the base current ideality factor is approximately 2. These experimental results agree well with a published theoretical calculation.<>     

The DC characteristics of GaAs/AlGaAs heterojunction bipolartransistors with application to device modeling

A complete DC model for the heterojunction bipolar transistor (HBT) is presented. The DC characteristics of the HBT are compared with the Ebers-Moll (EM) model used by conventional bipolar junction transistors (BJTs) and implemented in simulation and modeling programs. It is shown that although the details of HBT operation can differ markedly from those of a BJT, a model and a parameter extraction technique can be developed which have physical meaning and are exactly compatible with the EM models widely used for BJTs. Device I- V measurements at 77 and 300 K are used to analyze the HBT physical device performance in the context of an EM model. A technique is developed to extract the device base, emitter, and collector series resistances directly from the measured I-V data without requiring an ideal exp(qV_be/kT) base current as reference. Accuracies of the extracted series resistances are assessed. AC parameters of HBT are calculated numerically from the physical device structure. For modeling purposes, these parameters are shown to be comparable with those of conventional BJTs     

AlGaAs/GaAs heterojunction bipolar transistor decision circuit

An AlGaAs/GaAs heterojunction bipolar transistor (HBT) decision circuit has been designed and characterised for optical communications, using 3.5 mu m emitter width transistors with cutoff frequency of 27 GHz. The maximum bitrate for a BER of 10/sup -9/ was 4.2 Gbit/s. At 2.0 Gbit/s, the clock phase margin was 240 degrees .<>     

高亮度GaAlAs／GaAs双异质结红色发光二极管

报道了高亮度ＧａＡｌＡｓ／ＧａＡｓ双异质结红色发光二极管的制作和实验结果。该器件在２０ｍＡ工作电流下，最大发光强度约５００ｍｃｄ。     

Orientation effect on AlGaAs/GaAs heterojunction bipolartransistors

Orientation effects on N-p-n AlGaAs/GaAs heterojunction bipolar transistors (HBT's) have been demonstrated for the first time. We have observed that the current gains of HBT's fabricated on the same wafer are strongly dependent on the emitter direction. The HBT's with emitter direction of [010] show the highest current gain and the smallest emitter-size effect. This orientation effect could be attributed to the piezoelectric effect, which superposes the piezoelectric charges to the original emitter doping and generates the weak lateral electric field that drifts the injected carriers at the emitter periphery. The difference of the saturation voltage between collector-emitter of those HBT's corresponds to the superposed piezoelectric charges     

Temperature dependence of InGaP/GaAs heterojunction bipolartransistor DC and small-signal behavior

This work describes the temperature dependence of the DC and small-signal performance of InGaP/GaAs heterojunction bipolar transistors (HBT's) with different collector thicknesses. Detailed analyses of the small-signal performance and the temperature dependence of both DC and high-frequency parameters are presented. An HBT delay-time analysis is also presented and justified empirically. In addition, the factors causing the decrease in f_T with temperature are described, and the variations in collector resistance and collector drift velocity with temperature are determined     

Failure mechanisms in AlGaAs/GaAs power heterojunction bipolartransistors

We report the failure mechanisms resulting in the second breakdown characteristics found in AlGaAs/GaAs power heterojunction bipolar transistors (HBTs). The dominant failure mechanism is identified to be the increasingly larger base-collector leakage current at elevated junction temperatures. This failure mechanism is compared with those found in silicon bipolar transistors     

AlGaAs/GaAs heterojunction bipolar transistor circuits with improved high-speed performance

Using a self-aligned base contact process and proton implantation to reduce extrinsic base-collector capacitance, we have improved the high-speed performance of AlGaAs/ GaAs heterojunction bipolar transistor digital circuits. The cutoff frequency of the transistor fT with an emitter width of 2.0 ?m is 45 GHz. NTL ring oscillators have operated at 16.5 ps/gate and CML ring oscillators at 27.6 ps/gate. Frequency dividers (1/4) have operated up to 11 GHz with wafer-probe testing These are record speeds for bipolar circuits.