Effects of InGaP heteropassivation on reliability of GaAs HBTs

For the self-aligned AlGaAs/GaAs HBTs with the mesa-etched emitter, the instability of the surface states on the extrinsic base passivated by nitride is a major cause of the severe degradation of current gain. In this paper GaAs HBTs employing InGaP ledge emitter in order to passivate the surface of the extrinsic base and to reduce the surface states exhibited the considerable improvement of the current gain reliability with the activation energy of 1.97 eV and MTTF of 4.8×10⁸ h at 140°C. However, under the strong stress conditions InGaP/GaAs HBTs also produced the considerable degradation. The possible origins were investigated.     

4GHz300mW InGaP/GaAs HBT功率管研制

通过采用发射极-基极金属自对准、发射极镇流电阻,电镀空气桥等工艺改善了器件的高频特性,提高了器件热稳定性与功率特性.当器件工作在AB类,工作频率为4 GHz,集电极偏置电压为3.5 V时,尺寸为16×(3 μm×15 μm)的功率管获得了最大输出功率为24.9 dBm(309.0 mW)、功率增益为8.1dB的良好性能.     

A reliability comparison of InGaP/GaAs HBTs with and without passivation ledge

InGaP/GaAs heterojunction bipolar transistors (HBTs) with and without passivation ledge in the extrinsic base region were investigated. Gummel plot changes before and after reliability testing were compared. The experimental results demonstrated that the devices featuring the lower quality of the extrinsic base surface are more sensitive to a temperature–current stress. The HBTs with a passivation ledge have an activation energy of 1.41 eV and a mean time to failure (MTTF) of 10⁶ h whereas the HBTs without passivation ledge have an activation energy of 1.24 eV and a MTTF of 10⁵ h.     

A 5.7 GHz interpolative VCO using InGaP/GaAs HBT technology

A 5.7 GHz monolithic interpolative voltage-controlled oscillator using InGaP/GaAs HBT technology is demonstrated for the first time. Frequency tuning is achieved by changing the open loop gain instead of the tank capacitor. The experimental result showed that a 500 MHz tuning range at 5.7 GHz was realized, which can meet the requirement of 5.7 GHz ISM band     

Determination of thermal resistance using Gummel measurement for InGaP/GaAs HBTs

In this paper, we propose a technique to determine thermal resistance of InGaP/GaAs heterojunction bipolar transistors (HBTs). The technique is based on Gummel measurement at only a few substrate temperatures. The major advantage of this technique is the simplicity in measurement, since the temperature-dependent parameter does not need to be determined for each device size. Therefore, when a number of devices need to be measured, this technique is less time-consuming. Another feature of this technique is the separation of the thermal resistance and emitter resistance, so that it is easier to optimize the emitter resistance. The result shown in this paper is measured from an InGaP/GaAs HBT, and is compared with another typical technique.     

基区设计对InGaP/GaAs HBT热稳定性的影响

研究了不同基区设计对多发射极指结构功率InGaP/GaAs异质结双极型晶体管热稳定性的影响。以发生电流增益崩塌的临界功率密度为热稳定性判定标准,推导了热电反馈系数Φ、集电极电流理想因子η和热阻Rth与基区掺杂浓度NB、基区厚度dB的理论公式。基于TCAD虚拟实验,观测了不同基区掺杂浓度和不同基区厚度分别对InGaP/GaAs HBT热稳定性的影响。结合理论公式,对仿真实验曲线进行了分析。结果表明,基区设计参数对热稳定性有明显的影响,其影响规律不是单调变化的。通过基区外延层参数的优化设计,可以改进多指HBT器件的热稳定性,从而为多指InGaP/GaAs HBT热稳定性设计提供了一个新的途径。     

Low noise 5 GHz differential VCO using InGaP/GaAs HBT technology

The authors present the first InGaP/GaAs HBT differential VCOs with low phase noise performance. One is a cross coupled differential VCO, and the other is a Colpitts differential VCO. To achieve a fully integrated VCO, collector-base junction capacitance of HBT transistor is used for the frequency tuning varactor. The measured output frequency ranges of VCOs are 290 MHz and 190 MHz, and the phase noises at an offset frequency of 1 MHz are -118 dBc/Hz and -117 dBc/Hz respectively. The each VCO core dissipates 13.2 mW from a 3.5 V supply, and the output power is about -0.2 dBm. Concerned with cross coupled VCO, it shows the figure of merit of -179 dBc/Hz, which is the best result among the reported compound semiconductor FET and HBT VCOs.     

A K-band InGaP/GaAs HBT balanced MMIC VCO

A fully integrated K-band balanced voltage controlled oscillator (VCO) is presented. The VCO is realized using a commercially available InGaP/GaAs heterojunction bipolar transistor (HBT) technology with an f/sub T/ of 60 GHz and an f/sub MAX/ of 110 GHz. To generate negative resistance at mm-wave frequencies, common base inductive feedback topology is used. The VCO provides an oscillation frequency from 21.90 GHz to 22.33 GHz. The frequency tuning range is about 430 MHz. The peak output power is -0.3 dBm. The phase noise is -108.2 dBc/Hz at 1 MHz offset at an operating frequency of 22.33 GHz. The chip area is 0.84/spl times/1.00 mm/sup 2/.     

High reliability InGaP/GaAs HBT

Excellent long term reliability InGaP/GaAs heterojunction bipolar transistors (HBT) grown by metalorganic chemical vapor deposition (MOCVD) are demonstrated. There were no device failures (T=10000 h) in a sample lot of ten devices (L=6.4 μm ×20 μm) under moderate current densities and high-temperature testing (J_c=25 kA/cm ², V_ce=2.0 V, Junction Temp =264°C). The dc current gain for large area devices (L=75 μm ×75 μm) at 1 kA/cm² at a base sheet resistance of 240 ohms/sq (4×10 ¹⁹ cm^-3@700 Å) was over 100. The dc current gain before reliability testing (L=6.4 μm ×10 μm) at 0.8 kA/cm² was 62. The dc current gain (0.8 kA/cm²) decreased to 57 after 10000 h of reliability testing. The devices showed an f_T=61 GHz and f_max=103 GHz. The reliability results are the highest ever achieved for InGaP/GaAs HBT and these results indicate the great potential of InGaP/GaAs HBT for numerous low- and high-frequency microwave circuit applications. The reliability improvements are probably due to the initial low base current at low current densities which result from the low surface recombination of InGaP and the high valence band discontinuity between InGaP and GaAs     

Comprehensive Study of Emitter-Ledge Thickness of InGaP/GaAs HBTs

A comprehensive study of emitter-ledge thickness of InGaP/GaAs heterojunction bipolar transistors (HBTs) has been undertaken. It is shown that the recombination rate and electron densities are drastically increased near the exposed base surface between the base contact and the emitter ledge. In contrast, the corresponding hole densities are decreased. If the emitter ledge is too thick, current will flow through the undepleted ledge, which increases the emitter-size effect. In contrast, if the emitter ledge is too thin, it may not effectively passivate the surface. Therefore, the thickness of the emitter ledge is a crucial issue and should be carefully considered. It is shown that, from simulated and experimental results, the optimum emitter-ledge thickness of InGaP/GaAs HBT is 100-200 Aring     

High linearity InGaP/GaAs power HBTs by collector design

Improved power linearity of InGaP/GaAs heterojunction bipolar transistors (HBTs) with collector design is reported. The collector design is based on nonuniform collector doping profile which is to employ a thin high-doping layer (5/spl times/10/sup 17/ cm/sup -3//200 /spl Aring/) inside the collector (1/spl times/10/sup 16/ cm/sup -3//7000 /spl Aring/). The additional thin high-doping layer within the collector shows no obvious effects and impacts in dc characteristics and device fabrication if the layer was inserted close to the subcollector. For an HBT with a thin high-doping layer being inserted 4000 /spl Aring/ from the base-collector junction, the experimental result on third-order intermodulation demonstrates the significant reduction by as large as 9 dBc and improved IIP3 by 5 dB under input power of -10 dBm at frequency of 1.8 GHz.     

Polycrystal isolation of InGaP/GaAs HBTs to reduce collectorcapacitance

InGaP/GaAs heterojunction bipolar transistors (HBTs) with polycrystalline GaAs buried under the base electrode have been fabricated using low-temperature gas-source molecular beam epitaxy on SiO₂-patterned substrates. A cutoff frequency of 120 GHz and a maximum oscillation frequency of 230 GHz were obtained for three parallel 0.7×8.5 μm HBTs. Compared to HBTs without the polycrystal, the collector capacitance was reduced by 28% and the maximum stable gain was improved by 1.2 dB due to complete carrier depletion in the polycrystal under the base electrode. These results show the high potential of the proposed HBTs for high-speed digital and broadband-amplifier applications     

High-speed InGaP/GaAs HBTs using a simple collector undercuttechnique to reduce base-collector capacitance

High-speed InGaP/GaAs HBTs were fabricated using a simple collector undercut (CU) technique to physically remove the collector material underneath the extrinsic base region by selective etching for reducing base-collector capacitance (C_BC). The best HBTs achieved a f_T of 80 GHz and a f_max (MSG/MAG) of 171 GHz. To our knowledge, this is the highest f_max (MSG/MAG) ever reported for the InGaP/GaAs HBTs. Compared to the HBTs without CUs, the CU HBTs showed a factor of 1.38 times improvement in the highest achievable f_max (MSG/MAG) due to the significant reduction of the C_BC     

A new emitter design of InGaP/GaAs HBTs for high-frequencyapplications

An HBT (heterojunction bipolar transistor) structure using an AlGaAs-InGaP emitter is proposed. The AlGaAs-InGaP configuration introduces an electron launcher in the emitter and makes use of the velocity overshoot effect. This enhances the emitter transport and reduces the electron accumulation in the emitter. Simulations show that, by using the AlGaAs-InGaP structure, the emitter charging time can be greatly reduced compared to the conventional AlGaAs emitter design. As a result, the cutoff frequency can be substantially increased. A cutoff frequency of 235 GHz has been predicted     

Large-signal modeling and characterization of high-current effectsin InGaP/GaAs HBTs

High-current effects in InGaP/GaAs heterojunction bipolar transistors (HBTs) were modeled and characterized. In addition to the self-heating effect, high currents were found to degrade large-signal performance mainly through Kirk and quasi-saturation effects. New formalisms in terms of base transit time and base-collector diffusion capacitance were used to modify the conventional Gummel-Poon model. This new model was verified against large-signal characteristics measured at 2 GHz. The validity of the new model for HBTs of different emitter geometry was also explored     

低偏置电压工作的自对准InGaP/GaAs功率异质结双极晶体管

介绍L波段、低偏置电压下工作的自对准InGaP/GaAs功率异质结双极晶体管的研制.在晶体管制作过程中采用了发射极-基极金属自对准、空气桥以及减薄等工艺改善其功率特性.功率测试结果显示:当器件工作在AB类,工作频率为2GHz,集电极偏置电压仅为3V时,尺寸为2×(3μm×15μm)×12的功率管获得了最大输出功率为23dBm,最大功率附加效率为45%,线性增益为10dB的良好性能.     

低偏置电压工作的自对准InGaP/GaAs功率异质结双极晶体管

介绍L 波段、低偏置电压下工作的自对准In Ga P/ Ga As功率异质结双极晶体管的研制.在晶体管制作过程中采用了发射极-基极金属自对准、空气桥以及减薄等工艺改善其功率特性.功率测试结果显示:当器件工作在AB类,工作频率为2 GHz,集电极偏置电压仅为3V时,尺寸为2×(3μm×1 5 μm)×1 2的功率管获得了最大输出功率为2 3d Bm,最大功率附加效率为4 5 % ,线性增益为1 0 d B的良好性能     

A 25-GHz ultra-low phase noise InGaP/GaAs HBT VCO

A 25-GHz monolithic voltage controlled oscillator (VCO) has been designed and fabricated in a commercial InGaP/GaAs heterojunction bipolar transistor (HBT) process. This balanced VCO has a novel topology using a feedback /spl pi/-network and a common-emitter transistor configuration. Ultra-low phase noise is achieved: -106 dBc/Hz and -130 dBc/Hz at 100kHz and 1-MHz offset frequency, respectively. To the authors' knowledge, this is the lowest phase noise achieved in a monolithic microwave integrated circuit (MMIC) VCO at such high frequency. The single-ended output power is -1 dBm. It can be tuned between 25.33GHz and 25.75GHz using the base-collector junction capacitor of the HBT as a varactor. The dc power consumption is 90mW for a 9-V supply. An excellent figure-of-merit of -195 dBc/Hz is obtained.     

一种Ku波段宽调谐范围高输出功率的InGaP/GaAs HBT VCO

本文介绍了一种采用InGaP/GaAs HBT工艺实现的全集成应用于Ku波段的压控振荡器(VCO)。该VCO采用Colpitts结构,以达到宽调谐范围,并且该VCO取得了较高的输出射频功率。测试结果表明：该VCO的振荡频率为12.82 GHz～14.97 GHz,调谐范围为15.47%,输出射频功率为0.31 dBm～6.46 dBm,在载频13.9 GHz处相位噪声为-94.9 dBc/Hz@1 MHz。在5 V单电源直流偏置下该VCO的功耗为52.75 mW,其芯片尺寸为0.81 mm×0.78 mm。最后,本文对VCO的品质因数FOM指标进行了讨论。     

On the simulation of low-frequency noise upconversion in InGaP/GaAs HBTs

Residual phase-noise measurements of GaAs heterojunction bipolar transistors (HBTs) with different low-frequency noise properties are used to investigate how accurate a compact HBT model can predict the upconversion of low-frequency noise under nonlinear operation. We find that the traditional low-frequency source implementation, as well as a cyclostationary noise source implementation, have shortcomings under different operation conditions. While, in general, the cyclostationary approach yields much better results, it fails under certain operation conditions. Experimental evidence is given that this is caused by overestimated correlation between baseband noise and RF noise sidebands. It is shown that a model based on cyclostationary sources with reduced cross-correlation yields good agreement between measurement and simulation in all cases.