硅基雪崩光电探测器倍增层掺杂的研究

硅基雪崩光电探测器的器件性能与倍增层的掺杂浓度有着密切联系。研究了硅基雪崩光电探测器倍增层的掺杂浓度对雪崩击穿电压和光谱响应度等特性的影响。在硼的注入剂量由5.0×1012 cm-2减小为2.5×1012cm-2时,倍增层内电场强度逐渐降低,吸收区电场强度迅速增大,器件的雪崩击穿电压由16.3V迅速上升到203V,而光谱响应在95%的击穿电压下,峰值响应波长由480nm红移至800nm,对应的响应度由11.2A/W剧增到372.3A/W。综合考虑光谱响应和雪崩击穿电压的影响,在硼注入剂量为3.5×1012 cm-2时,可获得击穿电压为43.5V和响应度为342.5A/W的器件模型,对实际器件的制备具有一定参考价值。     

Injection photodiode based on an n-CdS/p-CdTe heterostructure

The possibility of developing injection photodiodes with a tunable/reconfigurable? photosensitivity spectrum in the spectral range of 500–800 nm based on an n-CdS/p-CdTe heterostructure is shown. It is established that such a structure in the short-wavelength region λ = 500 nm has the highest spectral sensitivity S _λ ≈ 3 A/W in the forward direction at a bias voltage of V = +120 mV and S _λ ≈ 2 A/W in the reverse direction at a bias voltage of V = ?120 mV. The integrated sensitivity of the device is S _int = 2 400 A/lm under illumination with white light E = 3 × 10^?2 lx, at a bias voltage of V = +4.6 V, and temperature of T = 293 K. Upon illumination with the monochromatic light of an LG-75 laser with the wavelength λ = 625 nm, S _int = ?1400 A/W (illumination power P = 18 × 10^?6 W/cm², bias voltage V = +4.6 V, and temperature T = 293 K). High values of S _λ and S _int provide the highly efficient transformation of light energy into electrical energy at low illumination levels (P < 18 × 10^?6 W/cm²).     

A graded-gap photoelectric detector for ionizing radiation

A heterostructure consisting of a graded-gap p-Al_xGa_1?xAs layer on an n-GaAs substrate is studied in relation to its role as a photoelectric-response detector of X-ray photons and α particles. It is found that the current-power sensitivity of the detector is as high as 0.13 A/W and the voltage-power sensitivity exceeds 10⁶ V/W. The effect of preliminary irradiation with 5.48-MeV α particles (²⁴¹Am) on the detector’s sensitivity is studied. It is established that the detector’s sensitivity is reduced by a factor of 1.5–2 after irradiation with α particles at a dose of 5 × 10⁹ cm^?2. A further increase in the radiation dose to 4 × 10¹⁰ cm^?2 does not affect the detector’s sensitivity.     

Monolithic Uncooled 8 × 8 Bolometer Arrays Based on Poly-SiGe Thermistor

This paper presents a monolithic uncooled 8 × 8 bolometer array with polycrystalline silicon-germanium (poly-SiGe) thermistors as active elements. The poly-SiGe films are deposited by ultrahigh vacuum vapor deposition (UHV/CVD) system and the dependence of the temperature coefficient of resistance (TCR) on annealing temperature has been investigated. To decrease the thermal conductance of the bolometer, the poly-SiGe thermistor was formed on a four leg suspended microbridge. The improved porous silicon micromachining techniques described here enable the integration of the bolometer array with the MOS readout circuitry. The measurements and calculations show that the mean responsivity is 1.07 × 10⁴ V/W with an uncorrected uniformity of 10.5% and a thermal response time of 10.5 ms, and the detectivity of 3.75 × 10⁸ cm Hz^1/2/W is achieved at a chopping frequency of 30 Hz and a bias voltage of 5 V.     

Injection photodiode based on a p-Si-n-CdS-n +-CdS structure

An injection photodiode with a high room-temperature rectification factor (10⁵) is developed based on a p-Si-n-CdS-n ⁺-CdS structure. It is shown that the light and dark current-voltage characteristics of the structure have identical features. It is found that the mode of “long” diodes is implemented in the structure at current densities of I = 10^?2?5 × 10^?4 A/cm²; in this case, the integral (S _int) and spectral (S _λ) sensitivities sharply increase. It is shown that S _int = 2.8 × 10⁴ A/lm (3 × 10⁶ A/W) for an illuminance of E = 0.1 lux and S _λ = 2.3 × 10⁴ A/W under laser irradiation with λ = 625 nm and a power of P = 10 μW/cm² at a bias voltage of V = 20 V. It is shown that the mechanism of photocurrent amplification is predominantly associated with ambipolar carrier-mobility modulation.     

Effects of NiO Layer on Anisotropic Magnetoresistance and Sensitivity of Ni81Fe19 Films

Magnetic thin films of Ta/NiO/Ni₈₁Fe₁₉/NiO/Ta were fabricated by a magnetron sputtering method. The effects of NiO layer thickness and substrate temperature on the anisotropic magnetoresistance (AMR) and the magnetic field sensitivity of these Ni₈₁Fe₁₉ films have been investigated. The results show that the AMR of 20-nm Ni₈₁Fe₁₉ film with 4-nm NiO achieves 5.02% at 450°C, while the magnetic field sensitivity achieves 9.00% × 10^?3 m A^?1 at the same conditions. These enhanced 40% and 230% comparing with the film without NiO layer, respectively.     

Minimization of leakage current of recessed gate AlGaN/GaN HEMTs by optimizing the dry-etching process

The backward current of Schottky contacts on unintentionally doped GaN samples prepared by different dry-etching methods was investigated. It was found that an ion beam etching (IBE) process with an accelerating voltage of 250 V under an angle of 20 degrees to minimize channeling achieves the best results. The backward current in this case is 4 × 10⁻¹⁰ A/μm² compared to the backward current of the unetched sample of 1 × 10⁻⁷ A/μm² at −100 V. With this process, recessed gate HEMTs on AlGaN/GaN heterostructures grown by low pressure MOVPE were fabricated and compared to HEMTs without recess. The applied gate recess etching technique improves the leakage current by nearly a factor of two. The maximum transconductance is improved from 40 mS/mm to 60 mS/mm at a gate length of 4 μm.     

Influence of neutron radiation on breakdown voltage of silicon voltage limiter

Experimental study of silicon voltage limiters?? breakdown voltage dependence on neutron radiation was conducted. It revealed that with increase of radiation density from 0.1×10¹⁴ to 2×10¹⁵ N/cm² the breakdown voltage monotonously increases: the smaller the breakdown voltage, the higher radiation density is needed to provide nominal breakdown voltage. Test curves which may be used for stabilization (normalization) of the breakdown voltage for samples with technological variations are suggested.     

IR photodetectors in the range of λ = 1.5–8 μm, based on silicon with multicharged nanoclusters of manganese atoms

It is demonstrated that infrared photodetectors based on silicon with multicharged nanoclusters of manganese atoms can be designed that operate in the wavelength range of ?? = 1.55?C8 ??m. Photodetectors fabricated on such materials have the following parameters: a spectral sensitivity range of ?? = 1.55?C8 ??m, an operating temperature range of T = 77?C250 K, an optimal electric field of E = 5 V/cm, an optimal size of V = 3 × 2 × 1 mm³, a sensitivity threshold of S = 10^?9 W/cm², and a response time of ?? < 10^?6 s.     

Industrial prospects of Pb1 − x Sn x Te:In with x > 0.3 solid solutions for photodetectors with extended sensitivity spectral range

Photoelectric properties of Pb_{1 ? x} Sn _x Te:In films with composition x > 0.3 in the temperature range from 4.2 to 80 K have been investigated. High sample sensitivity to black-body radiation has been discovered at the temperature of helium, and as the temperature of the radiation source decreases the sensitivity increases, which can be connected with the optical-frequency transition in the short-wavelength infrared and terahertz spectral range. The detectivity value D* = 8.2 × 10¹⁶ cm · Hz^1/2/W corresponding to the NEP = 3.1 × 10^?18 W/Hz^1/2, has been obtained at detector temperature 4.2 K and T _BBR = 15 K.     

An area-and-power-efficient 8.4-bit ENOB 30 MS/s SAR ADC in 65 nm CMOS

Area and power consumption are two main concerns for the electronics towards the digitalization of in-probe 3D ultrasound imaging systems. This work presents a 10-bit 30 MS/s successive approximation register analog-to-digital converter, which achieves good area efficiency as well as power efficiency, by using a symmetrical MSB-capacitor-split capacitor array with customized small-value finger capacitors. Moreover, simplified dynamic digital logic and a dynamic comparator have been designed. Fabricated in a 65 nm CMOS technology, the core circuit only occupies 0.016 mm². The ADC achieves a signal-to-noise ratio of 52.2 dB, and consumes 61.3 μW at 30 MS/s from a 1 V supply voltage, resulting in a figure of merit (FoM) of 6.2 fJ/conversion-step. The FoM defined by including the area is 0.1 mm² fJ/conversion-step.     

Nanoclay Paste as a Thermal Interface Material for Smooth Surfaces

A paste in the form of a polyol ester vehicle (liquid) containing 0.6 vol.% nanoclay is an effective thermal interface material. Nanoclay with a high conformability and hence a small bond line thickness is preferred, namely montmorillonite containing a quarternary ammonium salt organic modifier (dimethyl dehydrogenated tallow) at 125 meq/100 g clay, after exfoliation by using the vehicle. When it is used between smooth (0.009 μm) copper surfaces at a pressure of 0.69 MPa, the thermal contact conductance reaches 40 × 10⁴ W/m² K, in contrast to the corresponding values of 28 × 10⁴ W/m² K, 28 × 10⁴ W/m² K, 25 × 10⁴ W/m² K, and 24 × 10⁴ W/m² K previously reported for carbon black, fumed alumina, fumed zinc oxide, and graphite nanoplatelet pastes. Between rough copper surfaces (12 μm), the conductance provided by the nanoclay paste is slightly below those of the other pastes. The superiority of the nanoclay paste for smooth surfaces is attributed to the␣submicron bond line thickness; the inferiority for rough surfaces is due to the low thermal conductivity. The conductance provided by the nanoclay paste increases from 31 × 10⁴ W/m² K to 40 × 10⁴ W/m² K when the pressure is increased from 0.46 MPa to 0.92 MPa. This pressure dependence is stronger than that of any of the other pastes studied.     

Surface breakdown in silicon planar junctions—A computer-aided experimental determination of the critical field

Surface breakdown in silicon planar junctions is analysed with emphasis on the evaluation of the critical field (i.e., the maximum electric field within the depletion region at breakdown). This parameter is determined by a computer-aided experimental procedure consisting in relaxation field calculations with boundary conditions governed by junction breakdown voltage (at given gate voltage) as measured on specially processed gate-controlled diodes. The idealization (infinite doping) of the highly doped side of the junction, encountered in previous works, has been eliminated. Values of the critical field determined are in the range of 1 × 10⁶ V/cm (1·0 × 10⁶ V/cm for 1·0 μm gate-oxide and 1·4 × 10⁶ V/cm for 0·3 μm gate-oxide). These values are substantially higher than those estimated by other authors (5–6 × 10⁵ V/cm) and are consistent with independent experimental findings on avalanche (hot-carrier) injection in silicon diodes.     

A 10-bit 2.5-MS/s SAR ADC with 60.46 dB SNDR in 0.13-μm CMOS technology

This paper presents a 10-bit 2.5-MS/s successive-approximation-register (SAR) analog- to-digital-converter (ADC) design for micro controller unit of signal process system. Because of the proposed new segmented architecture of 7 MSBs-plus-3 LSBs capacitor–resistor hybrid digital-to-analog-converter using a thermometer decoder for the most significant 5 MSBs, this design achieves superior static nonlinearity and dynamic performance of SNDR, SFDR. Utilizing the proposed deviation calibration technique, the discharging and charging via substrate resulting from deviation of the comparator’s common-mode voltage is cancelled. The ADC is fabricated in a standard 1P5M 0.13-μm CMOS technology. The peak DNL and INL are +0.18/?0.20-LSB, +0.30/?0.25 LSB respectively while the ENOB is 9.52-bit around all process–voltage–temperature corner analysis. At a 2.3-V supply voltage and a 2.5-MS/s sampling rate, the ADC achieves a SNDR of 60.46 dB, SFDR of 75.32 dB while the power dissipation is 0.191-mW, that resulting in a figure of merit of 98.45 fJ/c-s. The die of ADC measures 0.51 × 0.20 mm² resulting in area efficiency of 122.6 μm²/code and compared with the benchmark SAR ADCs, this work is the most area efficient design.     

Characterization of a Bulk-Micromachined Membraneless In-Plane Thermopile

This paper describes the characterization method and results for bulk- micromachined in-plane thermopiles. Made of poly-Si or poly-SiGe, the thermocouple legs bridge the hot and cold side of a Si frame, which is formed by bulk micromachining. The characterization of the fabricated devices is carried out on a dedicated experimental setup, using which a uniform temperature difference can be imposed on all the thermocouples. Among design variations, the open-circuit output voltage reaches up to 95.0 mV/K and the corresponding output power on a matched external load is 2.34 × 10⁻³ μW/K². Two possible assembly schemes towards a fully fledged thermoelectric generator are illustrated as well. In the case of vertical assembly, the efficiency factor is expected to be 1.73 × 10⁻² μW/K²/cm².     

Surface photovoltage measurements for Cu,Ti and W determination in Si wafers

p-type (1 0 0) Cz silicon wafers were contaminated with Cu, W, and Ti in the dose range of 5×10⁹–1×10¹⁴ cm⁻² by ion implantation. Surface photovoltage measurements were used to detect the metal impurities after annealing. Fast and slow cooling have been used and calibration curves have been obtained in all cases. Higher sensitivity has been determined for slow cooling (Cu and W) or fast cooling (Ti) depending if deep levels are associated with substitutional (Cu and W) or interstitial (Ti) position.     

YBa2Cu3-xZnxO7薄膜红外探测器的研究

在对红外探测器进行理论分析的基础上,设计并研制了液氮温度下的Yba2Cu3-xZnxO7薄膜红外探测器,系统地测试了器件的特征参数.最好的结果为:对于波长为10μm,调制频率为f=500Hz,带宽为Δf=1Hz的红外输入辐射Rv(500,10,1)=3587V/W,NEP(500,10,1)=6.5×10-12W/Hz1/2,D*(500,10,1)=7.2×1012cmHz1/2/W,τ(500,10,1)=1.2ms.     

Thermal Conductivity Variation with Temperature for Lead-Free Ternary Eutectic Solders

The variations of the thermal conductivity with temperature for the lead-free ternary eutectic solders Bi-42.73 wt.%Sn-1.03 wt.%Ag (Bi-Sn-Ag), Sn-3.5 wt.%Ag-0.9 wt.%Cu (Sn-Ag-Cu), Sn-6 wt.%Sb-5 wt.%Ag (Sn-Sb-Ag), Sn-42.8 wt.%Bi-0.04 wt.%Cu (Sn-Bi-Cu), and In-48.4 wt.%Sn-2.31 wt.%Ag (In-Sn-Ag) were measured using a linear heat flow apparatus. It was observed that the thermal conductivities of solid phases for the Bi-Sn-Ag, Sn-Ag-Cu, Sn-Sb-Ag, Sn-Bi-Cu, and In-Sn-Ag solders decrease linearly with increasing temperature. The thermal conductivities of the Bi-Sn-Ag, Sn-Ag-Cu, Sn-Sb-Ag, Sn-Bi-Cu, and In-Sn-Ag solders at their melting temperature were obtained as 17.89 ± 1.6 W/K-m, 49.89 ± 4.5 W/K-m, 41.96 ± 3.8 W/K-m, 20.03 ± 1.8 W/K-m, and 70.21 ± 6.3 W/K-m, respectively. The thermal temperature coefficients for the Bi-Sn-Ag, Sn-Ag-Cu, Sn-Sb-Ag, Sn-Bi-Cu, and In-Sn-Ag solders were also determined to be ?2.894 × 10^?3 K^?1, ?0.907 × 10^?3 K^?1, ?1.246 × 10^?3 K^?1, ?2.638 × 10^?3 K^?1, and ?1.250 × 10^?3 K^?1, respectively, from plots of thermal conductivity versus temperature.     

新型量子光电探测器读出与显示

对一种响应近红外的新型量子光电探测器特性进行测试和分析,给出了2×8探测器阵列和读出电路的对接测试结果,设计初步的成像系统采集显示焦平面输出。探测器有一个-0.8V的阈值电压,偏压大于阈值电压后器件响应率远大于1A/W,且响应率随光照功率增大减小。2×8探测器阵列与设计的读出电路通过Si基板对接后在77K条件测试,读出电路的线性度好于99.5%,信噪比达到67dB,探测器偏压为-1.5V,积分时间为200μs时探测器率达到1.38×1010cmHz1/2/W,达到实际应用的要求。设计了数据采集卡和成像系统验证了对接样品的实用性。     

Heat Dissipation of Transparent Graphene Defoggers

In spite of recent successful demonstrations of flexible and transparent graphene heaters, the underlying heat‐transfer mechanism is not understood due to the complexity of the heating system. Here, graphene/glass defoggers are fabricated and the dynamic response of the temperature as a function of input electrical power is measured. The graphene/glass defoggers reveal shorter response times than Cr/glass defoggers. Furthermore, the saturated temperature of the graphene/glass defoggers is higher than for Cr/glass defoggers at a given input electrical power. The observed dynamic response to temperature is well‐fitted to the power‐balance model. The response time of graphene/glass defogger is shorter by 44% than that of the Cr/glass defogger. The convective heat‐transfer coefficient of graphene is 12.4 × 10^?4 W cm^?2 °C^?1, similar to that of glass (11.1 × 10^?4 W cm^?2 °C^?1) but smaller than that of chromium (17.1 × 10^?4 W cm^?2 °C^?1). The graphene‐based system reveals the lowest convective heat‐transfer coefficient due to its ideal flat surface compared to its counterparts of carbon nanotubes (CNTs) and reduced graphene oxide (RGO)‐based systems.