Decreased low frequency noise by hydrogen passivation of polysilicon emitter bipolar transistors

The effect of hydrogen passivation by forming gas annealing (FGA) on the bipolar junction transistor low frequency noise was investigated. The results demonstrated a reduced 1/f noise component by a factor of five after FGA, which resulted in a reduced corner frequency. An equivalent input noise spectral density (S_IB) dependence on base current (I_B) of S_IBI²_B and on emitter area (A_E) of S_IBA_E⁻¹ was observed, both before and after FGA. The interpretations of the results were (a) the 1/f noise was due to carrier number fluctuation, (b) the noise sources were homogeneously distributed over the polysilicon/monosilicon emitter interfacial oxide, and (c) the noise sources were passivated by hydrogen.     

1/f noise in n+-p-n microwave transistors

1/f noise measurements in the base current and the collector current of NEC 57807 n⁺-p-n microwave transistors show that the noise is not of the mobility fluctuation type, since the current dependence of S_IR(f) and S_IC(f) differs from the theoretical predictions. The low collector current 1/f noise makes it doubtful whether the mobility fluctuation concept is applicable in this case.     

High injection effects on noise characteristics of Si BJTs and SiGe HBTs

We present a physically based comparison of the current spectral densities in a SiGe heterojunction bipolar transistors (HBT) and a Si bipolar junction transistor (BJT) of identical geometry and doping levels, based on the direct evaluation of emitter, base and collector current fluctuations. An ensemble Monte Carlo (EMC) simulator self-consistently coupled with a 2D Poisson solver has been employed for the calculations. In the studied bias range, the largest reduction of the RF current noise values in the HBT as compared with the BJT derives from the spectral density of base current fluctuations, S_JB, and from the spectra of the cross-correlation between emitter and base current fluctuations, S_JBJE. This is due to the fact that the base current in the HBT is strongly reduced as a consequence of the lower gap of the SiGe base. At low injection, the collector spectral density S_JC exhibits a typical shot noise response while S_JB is governed by thermal noise. At high injection, the presence of hot carriers in the base–collector junction (which are less important in the HBT than in the BJT due to the SiGe/Si hetero-interface), the high carrier concentration in the base and the base push-out provokes the deviation of S_JC from the pure shot behavior. Under these conditions, the S_JB term can be neglected in the total noise analysis of the HBT for lower values of J_C, than in the BJT due to the Ge content benefits.     

Generation–recombination noise in bipolar transistors

The generation–recombination (g–r) noise in bipolar junction transistors (BJTs) is due to the deep-level impurities in the p–n junctions. The larger the amplitude of g–r noise, the worse the quality of BJTs, so that measuring the amplitude of the g–r noise is way of estimating the reliability of BJTs. In some papers, it is assumed that the amplitude of g–r noise is proportional to the square of base current (I_b²), but in a few papers it has been reported that this relation is more complex. In this paper the amplitude of g–r noise versus base current is discussed, the theoretical and experiment results demonstrate that the g–r noise and burst noise signal may be observed only in a certain range of base current, and the law S(f)∝I_b² is not valid. It means that we must measure g–r noise and observe burst noise signal over a wide range of base current to estimate the concentration of deep-level impurities in p–n junction and hence the reliability of BJTs.     

Temperature dependent IDS-VGS characteristics of an N-channel Si tunneling field-effect transistor with a germanium source on Si(110) substrate

在Si(110)衬底上制备了Ge源n型Si沟道隧穿场效应晶体管（TFET）。本文研究了温度对Ge源Si TFET器件的电学性能的影响。温度相关性研究显示器件漏电流主要由漏区的Shockley - Read - Hall (SRH) 产生于复合电流决定。器件开态电流随温度升高而增加,这是因为温度升高材料禁带宽度减小,隧穿几率增大。界面缺陷引起的隧穿电流的亚阈值摆幅随温度升高而变差,但是带间隧穿电流的亚阈值摆幅不随温度变化而变化。     

Low frequency noise in complementary npn and pnp polysilicon emitter bipolar junction transistors

Low frequency noise characteristics of high voltage, high performance complementary polysilicon emitter bipolar transistors are described. The influence of the base biasing resistance, emitter geometry and temperature on the noise spectra are discussed. The npn transistors studied exhibited 1/f and shot noise, but the pnp transistors are characterized by significant generation–recombination noise contributions to the total noise. For both types of transistors, the measured output noise is determined primarily by the noise sources in the polysilicon–monosilicon interface. The level of the 1/f noise is proportional to the square of the base current for both npn and pnp transistors. The contribution of the 1/f noise in the collector current is also estimated. The area dependence of 1/f noise in both types of transistors as well as other npn bipolar transistors are presented.     

Diagnostics of the quality of MOSFETs

The excess noise behaviour of silicided p-channel MOSFETs is investigated. Due to contact problems, generation-recombination noise spectra are observed. Analysis of the current noise spectra versus the current on a single device, showed that the generation-recombination noise was due to trapping of carriers in the source and drain contacts. An analysis of an L-array is not necessary to distinguish between channel and contact contribution. The classical geometry and current dependence of the noise is no longer valid if the noise in the series resistance is dominant. Large generation-recombination noise components, with the dependence S_I ∝ I⁴, point to poor device contact quality.     

InP/GaAs0.51Sb0.49/InP fully self-aligned double heterojunction bipolar transistors with a C-doped base: a preliminary reliability study

A preliminary reliability study is reported for carbon-doped InP/GaAs_0.51Sb_0.49/InP NpN double heterojunction bipolar transistors (DHBTs) lattice-matched to InP substrates. These DHBTs take advantage of the staggered (“type II”) band lineup at InP/GaAs_0.51Sb_0.49 interfaces: in this system, the GaAs_0.51Sb_0.49 base conduction band edge lies 0.15–0.18 eV above the InP collector conduction band, thus enabling the implementation of InP collectors free of the collector current blocking effect encountered in conventional Ga_0.47In_0.53As base DHBTs. The structure results in very low collector offset voltages, low emitter-base turn-on voltages, and very nearly ideal base and collector current characteristics with excellent junction ideality factors. Cut-off frequencies in excess of 100 GHz have been measured, making InP/GaAsSb DHBTs very attractive for wireless communication systems. InP/GaAs_0.51Sb_0.49 heterojunctions have so far received little attention in the literature, and no reliability information is available for this promising material combination. We have found that electrical stressing at moderate bias in fully self-aligned non-passivated devices results in a rapid, and reversible, degradation of device properties which is manifested through an increase of the base current ideality factor n_B. On the other hand, the collector current remains unchanged, indicating that there is no dopant migration effect under the test conditions used here.     

Improved performances of a two-step passivated heterojunction bipolar transistor

An interesting InGaP/GaAs heterojunction bipolar transistor (HBT) with a two-step passivated (ledge structure and sulfur treatment) process on the base surface has been fabricated and studied. Based on the two-step passivation, improved transistor characteristics including the specific contact resistances ρ_C, sheet resistances R_sh, base surface recombination current density J_SR, base current ideality factor n_B, and microwave performances are obtained. Furthermore, the device with two-step passivation reveals the better thermal stability on ρ_C, R_sh, and n_B than the devices with and without ledge structure. Therefore, the two-step passivation method can be employed for high-temperature and low-power electronics applications.     

Investigation of deep traps in silicon–germanium epitaxial base bipolar transistors with a single polysilicon quasi self-aligned architecture

The electrical properties of Si/Si_1−xGe_x bipolar transistors have been analysed at temperatures ranging from 77 to 500 K. The investigated SiGe base transistors were fabricated using a BiCMOS single-polysilicon quasi self-aligned process, where base implant had been replaced by selective epitaxy on the base active area. At low temperature, static current–voltage measurements show a degradation of base current ideality, whereas collector current remains ideal over the whole temperature range. By studying forward and reverse currents at emitter–base and base–collector junctions, we have established that deep levels were involved in conduction phenomena at these junctions. Detailed measurements using capacitance transient spectroscopy (with different reverse and filling pulse voltages and different filling pulse durations) have revealed the presence of two deep levels along the periphery of the emitter. These deep levels have been found with identical characteristics at both junctions. It is demonstrated that these traps are most probably induced by the extrinsic base implantation.     

Low-frequency noise in n-GaN

Low-frequency noise has been investigated in the hexagonal polytype of n-type gallium nitride (GaN) with equilibrium electron concentration at 300 K n ₀⋍7×10¹⁷ cm⁻³. The frequency and temperature dependence of the noise spectral density S _I/I² was studied in the range of analysis frequencies f from 20 Hz to 20 kHz in the temperature range from 80 to 400 K. Over the entire temperature range the frequency dependence of the dark noise is close to S _I/I²∼1/f (flicker noise). The rather weak temperature dependence of the noise level is characterized by very high values of the Hooge constant α⋍5–7. These large α values indicate a rather low level of structural quality of the material. The effects of infrared and band-to-band illumination on low-frequency noise in GaN are studied here for the first time. The noise level is unaffected by illumination with photon energy E _ph<E _g (E _g is the band gap) even for a relatively high value of the photoconductivity Δσ⋍50%. Band-to-band illumination (E _ph⩾E _g) influences the low-frequency noise level over the entire investigated temperature range. At relatively high temperatures the influence of illumination is qualitatively similar to that of band-to-band illumination on low-frequency noise in Si and GaAs. At relatively low temperatures the influence of illumination on the noise in GaN is qualitatively different from the results obtained earlier for Si and GaAs. Fiz. Tekh. Poluprovodn. 32, 285–289 (March 1998)     

Temperature dependences of surface recombination DC current–voltage characteristics in MOS structures

Temperature dependences of recombination current at interface traps in MOS transistor structure are investigated using the Shockley–Read–Hall Recombination DC current–voltage (R-DCIV) characteristics. Results include the effects of energy distribution of the interface traps (discrete, constant and U-shaped energy distributions) on the temperature dependence of the base terminal current-vs-gate-voltage lineshape (I_B–V_GB), the peak current and voltage (I_B-peak, V_GB-peak) and their thermal activation energy E_A, and the reciprocal slope n of the I_B-peak vs base/drain (or base/source) p/n junction forward voltage V_BD. Surface impurity concentration and oxide thickness are varied. Temperature dependence of E_A, V_GB-peak and n is small while I_B-peak and R-DCIV linewidth, large. This small temperature dependence simplifies the experimental implementation and data analysis of R-DCIV methodology applied at room temperatures without using expensive temperature controlled wafer-probe station.     

Temperature dependence of 1/f noise in polysilicon-emitter bipolar transistors

1/f noise was measured on polysilicon-emitter bipolar n-p-n and p-n-p transistors over a temperature range of 173K相似文献   

Change in d.c. and 1/f noise characteristics of n-submicron MOSFETs due to hot-carrier degradation

Hot-carrier stress and its influence on d.c. and 1/f noise characteristics in submicron n-channel MOSFETs was investigated. From a 0.5 μm CMOS technology we observed a negative shift in the threshold voltage and a decrease in the drain current. The degradation increases the series resistance on the drain side. In most cases, the relative 1/f noise in the drain current also increases. A degraded device is often found to be noisier in its reverse mode than in its normal mode. The novel material is that the normalized 1/f noise analysis in terms of the 1/f noise parameter α is a more sensitive diagnostic tool for hot-carrier degradation in submicron MOSFETs than S_I (

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) and some results are qualitatively explained in terms of mobility fluctuations.     

Some aspects of current gain variations in bipolar transistors

This paper deals with the study of the main mechanisms involved in the bipolar transistor current-gain variations.In the first part, we describe some properties of characteristic parameters N_S and I_SR of the surface “diode”; an attempt is made to explain the strong correlation between N_S and I_SR.In a second part, we analyse the influence of emitter current crowding, high injection in the base region, and base widening effects on the high level bias current gain value. Critical current densities beyond which each of these effects takes place are defined, allowing us to evaluate their comparative importance at a given collector current value. Our study shows that, on the one hand, for transistors affected by emitter-current crowding, the surface currents play an essential part in the high level bias current gain fall off and, on the other hand, the base widening effect has a very great influence on the static (I_C, V_EB) characteristic and on the emitter injection efficiency value.In the third part, the experimental results obtained are reported and compared with previously proposed analytical relations.     

Non uniform recombination in thin silicon-on-sapphire films

Recombination parameters of SOS films are deduced from the study of the magnetoconcentration effect in double-injecting structures. The method of measurement is based on an original theory succintly developed; it takes into account general SRH bulk and surface recombination laws; moreover inhomogeneous distributions of recombination centers are considered.Experimental results (current-voltage characteristics of such “magnetodiodes”), when analysed according to the proposed method, lead to more realistic values of the global recombination parameters (τ_v, S₁, S₂) of the SOS film. It is proved, for example, that the previous simplified analysis overestimates the carrier recombination velocity on the Si-Al₂O₃ surface. On the contrary our method gives both a moderate value for this recombination velocity and a lower carrier lifetime near the Sapphire interface, which well agrees with the continuity of recombination rates at the surface and in the underlying bulk; the higher recombination region is found to be 100–1000 Å thick.     

1200 V 4H-SiC Bipolar Junction Transistors with A Record β of 70

A common current gain of 70 has been achieved in 4H-SiC bipolar junction transistors (BJTs) at room temperature, which is the highest among those reported. BJTs having an active area of 4 mm × 4 mm exhibit a specific on-resistance of 6.3 mΩ cm² at 25°C, which increases to 17.4 mΩ cm² at 250°C. BV_CEO (the breakdown voltage from collector to emitter with open base) and BV_CBO (the breakdown voltage from collector to base with open emitter) of 1200 V were observed at <5 μA leakage currents at all temperatures up to 250°C. Dynamic characteristics were measured using the IXYS RF/Directed Energy IXDD415 gate driver evaluation board to drive the BJT. A collector current (I _C) rise time at turn-on of 32 ns was measured with a 1.6 A gate current provided to support the collector current of 63 A. An I _C fall time at turn-off of 16 ns was achieved.     

Influence of the manufacturing process on the electrical properties of thin (<4 nm) Hafnium based high-k stacks observed with CAFM

In this work, the dependence of the electrical characteristics of some thin (<4 nm) HfO₂, HfSiO and HfO₂/SiO₂ stacks on their manufacturing process is studied at the nanoscale. Topography, current maps and current–voltage (I–V) characteristics have been collected by conductive atomic force microscope (CAFM), which show that their conductivity depends on some manufacturing parameters. Increasing the annealing temperature, physical thickness or Hafnium content makes the structure less conductive.     

双外延基区4H-SiC BJTs的高温特性研究

基于4H-SiC的材料特性及双外延基区BJTs的工作原理,依据漂移扩散及复合理论,求解在考虑4种复合机制下的双极晶体管直流增益,并通过二维仿真模型对其在高温条件下的工作特性进行了计算分析。结果表明,随着温度的升高,基区离化率的增加会导致发射极注入效率下降,从而降低器件的直流增益。同时,SiC/SiO2 界面态及钝化层的质量会影响器件的表面复合速度,从而造成大电流下直流增益的显著下降。