MISiC高温氢气传感器研究

文章报道了采用NO直接氧化制备氮化氧化物作绝缘层，制备高灵敏度MISiC肖特基二极管式高温气体传感器的技术。采用NO直接氧化法，改善了器件的界面特性．实验结果显示，采用该方法制作的传感器具有高响应灵敏度和良好的响应重复性。     

新颖的氧化生长绝缘层的MISiC传感器特性研究

采用新颖的NO和O2 CHCCl3(TCE)氧化技术制备金属-绝缘-体SiC(MISiC)肖特基势垒二极管(SBD)气体传感器的栅绝缘层,研究了传感器的响应特性。结果表明,传感器可快速的检测低浓度的氢气,NO氮化氧化改善了绝缘层的界面,TCE工艺降低了界面态密度和氧化层的有效电荷密度,并同时提取重金属以提高传感器的性能,使其可在高温(如300℃)等恶劣环境下长期可靠的工作,研究还发现:适当增加绝缘层厚度有助于传感器灵敏度和可靠性的改进。     

紫外成像用高响应ZnS肖特基光电二极管阵列

基于分子束外延(MBE)生长技术,制备出了新颖的8×8 ZnS肖特基光电二极管阵列,研究了制备该器件的标准光刻,金属沉积,湿化学腐蚀,SiO2绝缘层沉积等一系列微电子处理工艺.该肖特基光电二极管阵列的光谱响应截止边为340nm.在400～250nm的可见光盲区域,光电响应测试显示该器件在截止边波长处具有0.15A/W的高响应度,相对应的量子效率为55%.成像测试显示该器件具有良好的紫外成像特性.     

紫外成像用高响应ZnS肖特基光电二极管阵列

基于分子束外延(MBE)生长技术,制备出了新颖的8×8 ZnS肖特基光电二极管阵列,研究了制备该器件的标准光刻,金属沉积,湿化学腐蚀,SiO2绝缘层沉积等一系列微电子处理工艺.该肖特基光电二极管阵列的光谱响应截止边为340nm.在400～250nm的可见光盲区域,光电响应测试显示该器件在截止边波长处具有0.15A/W的高响应度,相对应的量子效率为55%.成像测试显示该器件具有良好的紫外成像特性.     

在薄硅外延片上制备高频肖特基势垒二极管

采用超高真空化学气相沉积技术,在n型重掺Si衬底上生长了轻掺的薄硅外延层,利用扩展电阻和原子力显微分析对外延层进行了检验.结果表明,重掺Si衬底与薄硅外延层之间的界面过渡区陡峭,外延层厚度在亚微米级,掺杂浓度为10 1 7cm- 3.在此外延片上制备了高频肖特基二极管的原型器件,与传统的硅基肖特基二极管相比截止频率有了大幅提高     

在薄硅外延片上制备高频肖特基势垒二极管

采用超高真空化学气相沉积技术,在n型重掺Si衬底上生长了轻掺的薄硅外延层,利用扩展电阻和原子力显微分析对外延层进行了检验.结果表明,重掺Si衬底与薄硅外延层之间的界面过渡区陡峭,外延层厚度在亚微米级,掺杂浓度为1017cm-3.在此外延片上制备了高频肖特基二极管的原型器件,与传统的硅基肖特基二极管相比截止频率有了大幅提高.     

HfTiO氮化退火对MOS器件电特性的影响

采用磁控溅射方法,在Si衬底上淀积HfTiO高k介质,研究了NO、N2O、NH3和N2不同气体退火对MOS电特性的影响。结果表明,由于NO氮化退火能形成类SiO2/Si界面特性的HfTiSiON层,所制备的MOS器件表现出优良的电特性,即低的界面态密度、低的栅极漏电和高的可靠性。根据MOS器件栅介质(HfTiON/HfTiSiON)物理厚度变化(ΔTox)和电容等效厚度变化(ΔCET)与介质(HfTiON)介电常数的关系,求出在NO气氛中进行淀积后退火处理的HfTiON的介电常数达到28。     

基于气体绝缘层的FET式室温NO2传感器

采用电子束刻蚀、机械探针贴膜等方法，构筑了基于气体绝缘层结构的单根酞菁铜纳米线FET式NO2气体传感器。结果发现，在室温条件下，器件的检测极限为1×10–6（NO2体积分数），其灵敏度高达2 172%，该结果相比于薄膜气体传感器检测极限降至十分之一。除此之外，该器件在室温条件下可以恢复至基线，在低浓度、室温监测方面有着较好的优势。     

一种新型的6H-SiC MOS器件栅介质制备工艺

采用干 O2 +CHCCl3(TCE)氧化并进干 /湿 NO退火工艺生长 6H-Si C MOS器件栅介质 ,研究了 Si O2 /Si C界面特性。结果表明 ,NO退火进一步降低了 Si O2 /Si C的界面态密度和边界陷阱密度 ,减小了高场应力下平带电压漂移 ,增强了器件可靠性 ,尤其是湿 NO退火的效果更为明显。     

Ge/SiGe异质结构肖特基源漏MOSFET

制备了氧化铪(HfO2)高k介质栅Si基Ge/SiGe异质结构肖特基源漏场效应晶体管(SB-MOSFET)器件,研究了n型掺杂Si0.16Ge0.84层对器件特性的影响,分析了n型掺杂SiGe层降低器件关态电流的机理。使用UHV CVD沉积系统,采用低温Ge缓冲层技术进行了材料生长,首先在Si衬底上外延Ge缓冲层,随后生长32 nm Si0.16Ge0.84和12 nm Ge,并生长1 nm Si作为钝化层。使用原子力显微镜和X射线衍射对材料形貌和晶体质量进行表征,在源漏区沉积Ni薄膜并退火形成NiGe/Ge肖特基结,制备的p型沟道肖特基源漏MOSFET,其未掺杂Ge/SiGe异质结构MOSFET器件的空穴有效迁移率比相同工艺条件制备的硅器件的高1.5倍,比传统硅器件空穴有效迁移率提高了80%,掺杂器件的空穴有效迁移率与传统硅器件的相当。     

A new Pt/oxide/In/sub 0.49/Ga/sub 0.51/P MOS Schottky diode hydrogen sensor

A new and interesting Pt/oxide/In/sub 0.49/Ga/sub 0.51/P metal-oxide-semiconductor (MOS) Schottky diode hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations and at different temperatures are measured. The presence of dipoles at the oxide layer leads to an extra electrical field and the variation of Schottky barrier height. Even at room temperature, a very high hydrogen detection sensitivity of 561% is obtained when a 9090 ppm H/sub 2//air gas is introduced. In addition, an absorption response time less than 1 s under the applied voltage of 0.7 V and 9090 ppm H/sub 2//air hydrogen ambient is found. The roles of hydrogen adsorption and desorption for the transient response at different temperatures are also investigated.     

The $hbox{Pd/TiO}_{2}$/ $hbox{n}$-LTPS Thin-Film Schottky Diode on Glass Substrate for Hydrogen Sensing Applications

A $hbox{Pd/TiO}_{2}$/n-type low-temperature-polysilicon (n-LTPS) MOS thin-film Schottky diode fabricated on a glass substrate for hydrogen sensing is reported. The n-LTPS is an excimer-laser-annealed and $hbox{PH}_{3}$ -gas-plasma-treated amorphous-silicon (a-Si) thin film. At room temperature and $-$2-V bias, the developed MOS Schottky diode exhibited a high signal ratio of 1540 to 50 ppm of hydrogen gas, with a fast response time of 40 s, respectively. The signal ratio is better or comparable with that of other reported MOS-type hydrogen gas sensors prepared on Si or III–V compound substrate. In addition, the signal ratio is 7.6, 14, and 30 times over other interfering gases of $ hbox{C}_{2}hbox{H}_{5}hbox{OH}$, $hbox{C}_{2}hbox{H}_{4}$ , and $hbox{NH}_{3}$ at room temperature and a concentration of 8000 ppm at $-$2-V bias, respectively. Thus, the developed MOS Schottky diode shows promise for the future development and commercialization of a low-cost hydrogen sensor.      

Highly hydrogen-sensitive Pd/InP metal-oxide-semiconductor Schottkydiode hydrogen sensor

A highly hydrogen-sensitive Pd/InP metal-oxide-semiconductor (MOS) Schottky diode hydrogen sensor is presented. The role of donor level in the interfacial oxide layer replacing the amphoteric native defects leads to enhanced barrier height and high sensitivity. According to reaction kinetics studies, the maximum change in barrier height achieves 0.31 eV. Short response and recovery times in the transient characteristics demonstrate the high hydrogen adsorption and desorption rates at high temperatures     

Improved hydrogen-sensitive properties of MISiC Schottky sensor with thin NO-grown oxynitride as gate insulator

Thin oxynitride grown in NO at low temperature was successfully used as gate insulator for fabricating MISiC Schottky hydrogen sensors. Response properties of the sensors were compared with other MISiC Schottky sensors with thicker or no oxynitride. It was found that the thin oxynitride played an important role in increasing device sensitivity and stability. Even at a low H/sub 2/ concentration, e.g., 100-ppm H/sub 2/ in N/sub 2/, a significant response was observed, indicating a promising application for detecting hydrogen leakage. Moreover, a rapid and stable dynamic response on the introduction and removal of H/sub 2//N/sub 2/ mixed gas was realized for the sensor. Improved interface properties and larger barrier height associated with the thin oxynitride are responsible for the excellent response characteristics. As a result, NO oxidation could be a superior process for preparing highly sensitive and highly reliable MISiC Schottky hydrogen sensors.     

A new Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor

A new and interesting Pd-oxide-Al/sub 0.3/Ga/sub 0.7/As MOS hydrogen sensor has been fabricated and studied. The steady-state and transient responses with different hydrogen concentrations has been measured at various temperatures. Based on the large Schottky barrier height and presence of oxide layer, the studied device exhibits a high hydrogen detection sensitivity and wide temperature operating regime. The studied device exhibits the low-leakage current and obvious current changes when exposed to hydrogen-contained gas. Even at room temperature, a very high hydrogen detection sensitivity of 155.9 is obtained when a 9090 ppm H/sub 2//air gas is introduced. Furthermore, when exposed to hydrogen-contained gas at 95/spl deg/C, both the forward and reverse currents are substantially increased with increased hydrogen concentration. In other words, the studied device can be used as a hydrogen sensor under the applied bidirectional bias. Under the applied voltage of 0.35 V and 9090 ppm H/sub 2//air hydrogen ambient, a fast adsorption response time about 10 s is found. The transient and steady-state characteristics of hydrogen adsorption are also investigated.     

A new Pd-InP Schottky hydrogen sensor fabricated by electrophoretic deposition with Pd nanoparticles

In this letter, a new Pd-InP Schottky diode hydrogen sensor fabricated by electrophoretic deposition (EPD) combined with nanosized Pd particles is first proposed and demonstrated. Experimentally, the studied device exhibited excellent current-voltage rectifying characteristics with a large Schottky barrier height (SBH) of 829 meV. At 303 K, a high saturation sensitivity ratio of 38 was found under a very low hydrogen concentration of 15 ppm H/sub 2//air. As raising the hydrogen concentration to 1.0% H/sub 2//air, the SBH lowering of the studied devic"dq"e reached to 307 meV and the sensitivity ratio was high as 1.29/spl times/10/sup 5/ with a very rapid response, which far prevailed over those fabricated by the conventional thermal evaporation and electroless plating techniques. Consequentially, the EPD Pd-InP Schottky diode with extremely effective Pd gate is promising for the fabrication of high-performance hydrogen sensors.     

Hydrogen sensors based on AlGaN/AlN/GaN HEMT

Pt/AlGaN/AlN/GaN high electron mobility transistors (HEMT) were fabricated and characterized for hydrogen sensing. Pt and Ti/Al/Ni/Au metals were evaporated to form the Schottky contact and the ohmic contact, respectively. The sensors can be operated in either the field effect transistor (FET) mode or the Schottky diode mode. Current changes and time dependence of the sensors under the FET and diode modes were compared. When the sensor was operated in the FET mode, the sensor can have larger current change of 8 mA, but its sensitivity is only about 0.2. In the diode mode, the current change was very small under the reverse bias but it increased greatly and gradually saturated at 0.8 mA under the forward bias. The sensor had much higher sensitivity when operated in the diode mode than in the FET mode. The oxygen in the air could accelerate the desorption of the hydrogen and the recovery of the sensor.     

Hydrogen sensing performance of Pt?oxide?GaN Schottky diode

An interesting Pt-oxide-GaN MOS-type Schottky diode hydrogen sensor with high-sensitivity hydrogen detection over a wide operating temperature regime is demonstrated. Experimentally, a voltage shift of 264.4 mV at a forward current of 1 mA is obtained under 5040 ppm H₂/air gas. Also, a large current variation of 0.89 mA in magnitude between air and 5040 ppm H₂/air gas is observed under a forward voltage of 0.2 V. Under an inert environment (N₂), a so-called Temkin isotherm can be used to interpret the hydrogen adsorption behaviour at the Pt-oxide interface.     

Sensing behavior and mechanism of titanium dioxide-based MOS hydrogen sensor

A Pd/TiO₂/Si MOS sensor (Pdtisin sensor) is proposed for the detection of hydrogen gas. The sensor is fabricated on a p-type 1 1 1 silicon wafer having resistivity of 3–6 Ω cm. The thickness of TiO₂ in this structure is about 600 nm. The capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics of the device is observed on the exposure of hydrogen gas at room temperature. The mechanism of hydrogen sensing of titanium dioxide-based MOS sensor (MOS capacitor) has been investigated by evaluating the change in flat-band voltage (V_FB) and fixed surface state density of the device in presence of hydrogen gas. The device exhibits very large parallel shift in C–V as well in G–V characteristics. The possible mechanism on Pd/TiO₂ and TiO₂/Si surface in presence of hydrogen gas has been proposed. The response and recovery time of the device is also measured at room temperature.     

Hydrogen-sensitive characteristics of a novel Pd/InP MOS Schottkydiode hydrogen sensor

Steady-state and transient hydrogen-sensing characteristics of a novel Pd/InP metal-oxide-semiconductor (MOS) Schottky diode under atmospheric conditions are presented and studied. In presence of oxide layer, the significant increase of barrier height improves the hydrogen sensitivity even at lower operating temperatures. Even at a very low hydrogen concentration environment, e.g., 15 ppm H₂ in air, a significant response is obtained. Two effects, i.e., the removal of Fermi-level pinning caused by the donor level in the oxide and the reduction of Pd metal work function dominate the hydrogen sensing mechanism. Furthermore, the reaction kinetics incorporating the water formation upon hydrogen adsorption is investigated. The initial heat of adsorption for the Pd/oxide interface is estimated to be 0.42 eV/hydrogen atom. The coverage dependent heat of adsorption plays an important role in hydrogen response under steady-state conditions. In accordance with the Temkin isotherm behavior, the theoretical prediction of interface coverage agrees well with the experimental results over more than three decades of hydrogen partial pressure