Gain of a heterojunction bipolar phototransistor

Analytical expressions have been derived for the collector current, optical gain, and quantum efficiency for a heterojunction, bi-polar phototransistor (HPT). These expressions can be utilized to optimize the current gain and quantum efficiency for HPT design. The presence of avalanche multiplication in the base-collector junction has been taken into account and shown to be a significant factor in determining the gain of an InGaAs/InP phototransistor. Experimental results of optical gain versus the collector-emitter voltage can only be explained in terms Of avalanche multiplication.     

双异质结单载流子传输光敏晶体管输出电流

详细对比并分析了双异质结单载流子传输光敏晶体管(Uni-travelling-carrier Double Heterojunction Phototransistor,UTC-DHPT)与单异质结光敏晶体管(Single Heterojunction Phototransistor,SHPT)在大的入射光功率范围下集电极输出电流特性.首先,UTC-DHPT仅选取窄带隙重掺杂的基区作为吸收区,与SHPT选取基区和集电区作为吸收区相比,其光吸收区厚度小,在小功率入射光下UTC-DHPT的输出电流小于SHPT的输出电流.其次,由于UTCDHPT的双异质结结构,光生电子和光生空穴产生于基区,减弱了SHPT因光生空穴在集电结界面积累而产生的空间电荷效应,避免了SHPT在小功率入射光下输出电流开始饱和的问题,从而UTC-DHPT获得了比SHPT更大的准线性工作范围.最后,UTC-DHPT的单载流子(电子)传输方式使得基区产生的光生空穴以介电弛豫的方式到达发射结界面,有效降低了发射结势垒,增加了单位时间内由发射区传输到基区的电子数量,提高了其发射结注入效率,在大功率入射光下UTC-DHPT比SHPT能获得更高的输出电流.     

Integrated optical devices of InGaAsP/InP heterojunction phototransistor and inner stripe light-emitting diode

New integrated optical devices combining an InGaAsP/InP HPT and an inner-stripe LED are proposed and their fabrication processes are described. The device functions of light amplification, optical bistability, and optical switching are demonstrated in the 1-μm wavelength region.     

Integrated optical devices of InGaAsP/InP heterojunction phototransistor and inner stripe light-emitting diode

New integrated optical devices combining an InGaAsP/InP HPT and an inner-stripe LED are proposed and their fabrication processes are described. The device functions of light amplification, optical bistability, and optical switching are demonstrated in the 1-µm wavelength region.     

Gain and frequency response of a graded-base heterojunction bipolar phototransistor

A study has been made of the carrier transport and optical gain of a heterojunction bipolar phototransistor in the presence of a drift field in the base region. The computational method employed is based on transfer matrices for minority-carrier density in the base region in the presence of ionizing radiation. Scattering matrices for the electron and hole currents are used for computing the avalanche multiplication in the collector junction. The effect of varying the ratio of absorption in the base region to that in the collector has been examined. The expressions derived have been used to estimate the frequency response of the bipolar heterojunction phototransistor.     

Numerical analysis of SiGe heterojunction bipolar phototransistor based on virtual substrate

SiGe heterojunction bipolar phototransistors based on Si_1?yGe_y virtual substrate have been proposed in this paper. The current gain and external quantum efficiency of the heterojunction bipolar phototransistors are calculated by solving one-dimensional diffusion equations. The computed results show that external quantum efficiency increases with the increase of Ge content of Si_1?yGe_y virtual substrate and a high external quantum efficiency of 142 can be obtained in the heterojunction bipolar phototransistor with ten periods of Ge/Si_0.4Ge_0.6 multi-quantum wells on virtual substrate with Ge content of 0.6. The dependences of external quantum efficiency and current gain on structure parameters of the heterojunction bipolar phototransistors are investigated in detail. It is useful for design and optimization of the heterojunction bipolar phototransistors.     

Preparation and properties of Zn delta-doped GaAs/AlGaAs heterojunction phototransistor

We have prepared, characterized and discussed the performance of AlGaAs/GaAs heterojunction bipolar phototransistor (HPT) including Zn delta-doped base. Due to the existence of δ-doped sheets located in the middle of undoped GaAs base the δ-doped HPT devices exhibit low dark current, nearly zero offset voltage, saturation voltage ∼0.4 V, and rise and fall times in ns range at wavelength of 850 nm up to 6 V of applied voltage. Due to avalanche multiplication behavior at the collector junction, an increased optical gain G>10 can be reached for applied voltages in the range of 6-12 V. For voltages higher than the device breakdown voltage (∼12 V) switching and negative differential resistance (NDR) effect is measurable in the inverted mode of operation.     

High-density data-retention power gating structure using a four-terminal double-gate device

This paper presents a new power gating structure with robust data retention capability using only one single double-gate device to provide both power gating switch and virtual supply/ground diode clamp functions. The scheme reduces the transistor count, area, and capacitance of the power gating structure, thus improving circuit performance, power, and leakage. The scheme is compared to the conventional power gating structure via mixed-mode physics-based two-dimensional numerical simulations. Analysis of virtual ground bounce for the proposed scheme is also presented.     

Operation of a ballistic heterojunction permeable base transistor

A ballistic heterojunction permeable base transistor (HPBT) is proposed and an analytical and numerical analysis of the device is performed. The new feature of the device structure is an AlGaAs hetero-emitter for injection of hot electrons into a 150-nm-thick GaAs base layer. A tungsten grating is embedded in the base layer and the Schottky depletion around the metal wires controls the vertical current. In this investigation, it is established that the high velocity of the hot electrons will prevent charge accumulation in the base layer. Thereby the dependence of the doping on the transconductance is lower than for the permeable base transistor. The HPBT is expected to have a unity-current gain cut-off frequency above 300 GHz     

Phase dynamics of a timing extraction system based on an optically injection-locked self-oscillating bipolar heterojunction phototransistor

We describe the phase dynamics of a timing extraction system based on direct optical injection locking of a multifrequency oscillator employing an InGaAs/InP heterojunction bipolar phototransistor. We present a general model for the locking range, jitter transfer function, and output phase noise. The model is confirmed by a series of locking experiments. We consider first fundamental timing extraction, that is, a 10-GHz oscillator extracting the clock from a 10-Gbit/s data stream. Second, we address superharmonic timing extraction where 40-Gbit/s data lock the fourth harmonic of the 10-GHz oscillator. In the superharmonic timing extraction case, a clock is extracted at 40 GHz as well as its subharmonics at 10, 20, and 30 GHz.     

Operation characteristics of three-terminal hybrid structure with multiple-quantum-well reflection modulator and heterojunction phototransistor

The operation characteristics of optically controlled three-terminal gates consisting of a multiple quantum well (MQW) reflection modulator and a heterojunction phototransistor (HPT) are discussed. It is found that the photonic gates, in which both components are electrically connected in series and parallel, operate as NOR and OR gates, respectively. The photonic gates exhibit a high contrast ratio of more than 20 dB as well as optical gain.<>     

Demonstration of enhanced performance of an InP/InGaAsheterojunction phototransistor with a base terminal

The optical gain and the small-signal frequency response of an InP/InGaAs heterojunction phototransistor (HPT) with a base terminal are investigated in detail for the first time. When operated under an optimally chosen external base current, the optical gain is enhanced more than five times over that of the same device operated as a two-terminal device, over a 17-dB range of input optical power. The small-signal 3-dB bandwidth of the three-terminal device is enhanced 15 times over that of the two-terminal device over the same range of input optical power. For a pseudorandom NRZ bit stream at 100 Mb/s, a clear eye opening is observed at an incident optical power of -33 dBm (500 nW)     

High-gain and very sensitive photonic switching device byintegration of heterojunction phototransistor and laser diode

A photonic switching device with very large gain and high sensitivity has been developed by the vertical and direct integration of a heterojunction phototransistor and a laser diode. The device switches on with very low input power of ~10 nW and emits output power of ~4 mW under continuous-wave conditions at room temperature. The minimum energy for switching on is estimated to be as low as 80 fJ. The internal optical feedback of the device is quantitatively discussed to interpret the low-power operation for the switch-on     

Low power WTA circuit for optical position detector

A time domain winner take all (WTA) circuit for a 1D optical position detector is presented. The circuit implements a new asynchronous technique which estimates the position of a light spot impinging on the sensor with sub-pixel resolution. This technique first detects the peak of the light spot, then, starts a new competition, by eliminating the winner pixel. In this way the sensor asynchronously dispatches the pixels in order to reconstruct the spot profile. The simulated circuit shows a total power consumption of about 15.6 muW at 3.3 V, while the average dynamic power consumption needed to implement one step of the algorithm, can be estimated to be about 0.4 nW     

The application of heterojunction structures to optical devices

Basic factors are reviewed that enter into the successful operation of single crystal heterojunction devices, with an emphasis on the role of defects. The devices discussed include laser diodes, solar cells and electron emitters using negative electron affinity surfaces.     

基于光子晶体平板传导共振模的低功率光开关

利用严格耦合波算法计算了二维光子晶体平板结构随角度变化透过谱和波长变化透过谱,研究了透过谱上传导共振峰与二维光子晶体平板能带结构的关系。利用共振传导模的低透过和高Q值的特点,设计了基于磷化铟材料的工作在1550nm波长附近的角度分辨和波长分辨的光子晶体光开关。理论模拟结果表明,该结构透过谱上传导共振峰品质因子可达105,非线性折射率变化为10-4即可实现开关对比度接近100%。当信号光或泵浦光分别与光子晶体平板传导共振模耦合时,由于共振耦合使得泵浦光场增强,需要泵浦能量仅为184fJ,为目前所知能量最低的光开关。     

Improved power performance for a recessed-gate AlGaN-GaN heterojunction FET with a field-modulating plate

A recessed-gate AlGaN-GaN field-modulating plate (FP) field-effect transistor (FET) was successfully fabricated on an SiC substrate. By employing a recessed-gate structure on an FP FET, the transconductance was increased from 150 to 270 mS/mm, leading to an improvement in gain characteristics, and current collapse was minimized. At 2 GHz, a 48-mm-wide recessed FP FET exhibited a record output power of 230 W (4.8 W/mm) with 67% power-added efficiency and 9.5-dB linear gain with a drain bias of 53 V.     

High-frequency characterization of heterojunction bipolartransistors using numerical simulation

The high-frequency performance of semiconductor devices is estimated using a small-signal numerical calculation based on drift-diffusion equations. In particular, unity current gain frequency in the common-emitter configuration (f_T) and maximum frequency of oscillation (f_max) are calculated for a heterojunction bipolar transistor. f_max is calculated from numerically obtained y parameters using formulas for maximum available gain, Mason's invariant (U), and a passivity criterion. They all give the same value for f_max. The influence of extrinsic and intrinsic base resistance on f_max is investigated for one device design. It is also found that a frequency used approximation formula for f_max is inaccurate, especially at higher current levels     

The optical and detector properties of the PbS-Si heterojunction

Related optical and detector properties of the PbS-Si heterojunction (HJ) are presented and discussed. A direct optical bandgap at 300 K of 0.44 eV has been measured for PbS-Si versus 0.42 eV for PbS-sapphire. The HJ photocurrent frequency response has been determined to consist of two waveform components: Type A, a "spike" present only during the turn-on and turn-off stages of a radiation pulse, is bias independent; Type B, a continuous response, which increases with reverse bias. The temperature characteristic of the photocurrent has been observed to be strongly dependent on which waveform type dominates. The HJ noise current is Johnson noise limited at zero bias and 1/fnoise limited under reverse bias. The HJ dark current is postulated to have four main generation mechanisms depending on temperature: Si-generated current, diffusion current from the PbS, PbS depletion or surface-generation current, and surface leakage. The PbS-Si HJ spectral response combines the effect of intrinsic absorption in Si and PbS and transitions between the Si and PbS valence bands. A detectivity of 1 × 10¹¹cm . Hz^1/2/W has been obtained at 3 µm.     

Electrical characterization of cobalt phthalocyanine/p-silicon heterojunction

We report the fabrication of organic/inorganic heterojunction of cobalt phthalocyanine (CoPc) with p-type silicon (p-Si) using vacuum thermal evaporation. At ambient conditions, the electrical characteristics of the heterojunction are investigated. The optical band gap of CoPc is calculated from absorption spectrum using Tauc׳s law. The electrical characterization of the heterojunction shows rectifying behavior with a rectification ratio (RR) of 316. Different diode parameters are extracted from the current–voltage (I–V) curves, such as ideality factor n, barrier height ϕ, series resistance R_s and shunt resistance R_sh. These parameters are in good agreement with those calculated from the functions of Cheungs and Norde . The conduction of charge carriers through the interface of p-Si/CoPc is also studied. The fabricated heterojunction could be a promising candidate for its potential use in electronic applications.