硅的低温电学性质

本文在20°—300°K研究了室温载流子浓度2×10¹²—1×10²⁰cm^-3含硼或磷(砷)Si的电学性质。对一些p-Si样品用弱场横向磁阻法及杂质激活能法进行了补偿度的测定,并进行了比较。从霍尔系数与温度关系的分析指出,对于较纯样品,硼受主能级的电离能为0.045eV,磷施主能级为0.045eV,在载流子浓度为10¹⁸—10¹⁹cm^-3时发现了费米简并,对载流子浓度为2×10¹⁷—1×10¹⁸cm^-3的p-Si及5×10¹⁷—4×10¹⁸cm^-3的n-Si观察到了杂质电导行为。从霍尔系数与电导率计算了非本征的霍尔迁移率。在100°—300°K间,晶格散射迁移率μ满足关系式AT^-a,其中A=2.1×10⁹,α=2.7(对空穴);或A=1.2×10⁸,α=2.0(对电子)。另外,根据我们的材料(载流子浓度在5×10¹¹—5×10²⁰cm^-3间),分别建立了一条电阻率与载流子浓度及电阻率与迁移率的关系曲线,以提供制备材料时参考之用。     

80—500°K间InSb的电导率、霍尔效应及磁阻效应

文中报导了80—500°K间n型及p型InSb的电导率、霍尔系数及磁阻效应的测量,所用样品的杂质含量(补偿后)为4×10¹³—7×10¹⁷cm^-3。由结果的分析得出InSb的本征载流子浓度、禁带宽度及电子迁移率等数值,讨论了电子的散射机构以及强磁场下磁阻与磁场强度成一次方正比关系的可能原因。     

证实GaAs中深能级陷阱发射到间接导带的极小的新技术

本文对具有深能级陷阱的肖特基势垒耗尽区的C-V特性提供了一种新的分析,得到了能带图中能级的绝对位置。发现了通常在气相外延GaAs中观察到的0.83±0.005eV电子陷阱位于Γ导带极小下0.543eV(240K)和0.537eV(120K)处。表明这些能级能发射电子到L极小,而且与这些极小有关的参数具有零的温度系数。这些中心的俘获截面是σ∽=(1.8±0.4)×10~(-14)cm~2,在120—240K整个温度区域有一个零的激活能。     

ZnSe晶体中Mn2+离子的能级

研究了ZnSe:Mn的光导激发谱.室温下观察列两个峰:4600Å和5380Å.还研究了4400Å及5200Å激发下光导与温度的关系.根据这些实验认为:Mn2+离子的第一激发态4T1,非常接近导带.理论上导出了5200Å激发下光导对温度的依赖.调节参数将理论与实验进行拟合.从选定参数中得出:Mn2+的4T1态位于导带下0.054eV.4400Å激发下光导与况度的关系用陷阱的作用解释.陷阱深度估计为0.4eV.     

掺磷的硅中电子自旋共振

本文叙述了在室温、液N₂和液H₂及其降压温度下,利用3厘米波段双重调制波谱仪对掺磷原子浓度为～10¹⁵—～10¹⁸/厘米³的硅样品进行的电子自旋共振研究,文中还简述了低温控制系统。实验观察到传导电子、表面缺陷中心和电子-核超精细结构谱线,以及有效电子-施子核对的互作用谱线,并获得相应的g因子。在14°K下,得到施主核上电子波函数幅度的平方|Ψ(0)|²和电子-核超精细互作用常数α_D,与G.Feher在1.25°K下利用电子-核双共振方法得到的结果相近。     

红色Hgl_2中激子-电子和激子-空穴相互作用

在N_2激光的强激发下研究了纯的红色HgI_2的光致发光光谱。所用HgI_2是层状的半导体,具有2.4eV的直接能带隙。光谱呈现出激子-空穴的相互作用,也呈现出激子-电子的相互作用。 脉冲强激发引起两条发射带(在150°K温度下为2.280eV和2.226eV)。当温度超过60°K时,发射强度随激发强度按平方规律增长。当温度降到60K以下时,另一个位于     

全无机钙钛矿CsPbBr3微米棒的变温荧光特性

通过化学气相沉积法(CVD)在云母基底上制备得到CsPbBr3微米棒,并使用扫描电子显微镜(SEM)、X射线衍射(XRD)对样品形貌和晶体结构进行表征.采用变温(10～290 K)荧光光谱研究了CsPbBr3激子发光的温度依赖特性.实验发现,在室温下CsPbBr3微米棒有两个发光峰,分别为位于2.357 eV、半宽为5...     

本征富受主型ZnO微米管光致发光的温度调控机制

热效应是影响半导体器件发光性能的最关键因素之一.本文针对光学气化过饱和析出法制备的本征富受主型ZnO微米管,系统研究了其光致发光的温度调控机制.研究表明,所制备ZnO微米管具有规则的六边形截面形貌,长度达5 mm、直径达100μm,室温下的光学带隙约为3.30 eV;随着环境温度的提高,其光致发光强度呈现"热淬灭-负热淬灭-热淬灭"的反常变化.在80—200 K温区内的热淬灭行为与浅施主的退/电离、自由激子热离化以及中性受主束缚激子的转变有关;在200—240 K温区内发生的负热淬灭行为与导带底以下488 me V处深能级陷阱上电子的热激发有关;在240—470 K温区内发生的热淬灭行为则与导带底以下628 me V处非辐射复合中心的Shockley Read-Hall复合有关.非辐射复合中心和陷阱中心的形成均与本征富受主型ZnO微米管的氧空位缺陷有关.上述研究结果在高温高效富受主型ZnO微米管基光电器件的设计与研发方面具有重要指导意义.     

电子型超导体Sm2-xCexCuO4(0.00≤x≤0.21)的异常热电势与电阻率

测量了Sm2-xCexCuO4(0.00≤x≤0.21)多晶样品的热电势S和电阻率ρ的温度依赖关系.在缘绝体-金属转变边界处,观测到热电势从绝缘体区明显的弱温度依赖关系到金属区线性温度依赖关系的转变.当Ce的含量由0.09增加到0.21时,高温下S的斜率发生由负到正的转变,这是能带的填充能级发生改变时电子型和空穴型载流子的贡献发生竞争的表现,由电子型向空穴型的过渡发生在x＝0.17处.S和ρ在200K以下的斜率变化是载流子局域化造成的.x＝0.06-0.21的样品在50K处观察到一个正的曳引峰.室温下的热电势S300K和S0(高温区热电势线性外推到0K的值)与Ce含量在绝缘体、欠掺杂和过掺杂区域有不同的依赖关系.过掺杂区域很小的S300K和S0意味着一个宽带的费米液体的贡献,同时ρ满足T2关系,二者相一致.     

等离子MOCVD系统生长ZnO薄膜掺N2和掺NH3特性比较

利用MOCVD方法生长了高质量的ZnO薄膜材料,分别通过N2和NH3对c面和R面蓝宝石衬底上生长的ZnO薄膜材料进行了掺杂行为研究.掺N2时,X射线衍射半峰全宽仅为0.148°,室温光荧光发光峰位于3.29eV,半峰全宽～100meV,电阻率由0.65 Ω·cm增大到5×l04Ω·cm.掺NH3时,X射线衍射峰半峰全宽0.50°,样品为弱p型,电阻率为102Ω·cm,载流子浓度为1.69×1016 cm-3.同时我们还观察到弱p型材料很容易退化成n型高阻材料.     

Recombination parameters in low-resistivity gamma-irradiated η-type germanium

Studies of recombination in ～0.2 Ω-cm As- and Sb-doped Co⁶⁰ γ-irradiated Ge which yield energy levels and the temperature dependence of the electron and hole capture probabilities are reported. For Sb-doped material at 323°K, the recombination center energy level position (neglecting statistical weight) was found to be 0.361±0.005 eV above the valence band with a possible slight temperature dependence corresponding roughly to one-half the variation of band gap with temperature. The capture probability ratio at this same temperature was 740. For the Asdoped case, two different levels appear to dominate the recombination process in annealed and unannealed low resistivity material. The energy level positions relative to the valence band (neglecting statistical weight) are 0.327±0.005 eV and 0.37±0.01 eV at room temperature for the annealed and unannealed samples, respectively. The corresponding capture probability ratios are 650 and 810. As in the case of Sb-doping, the energy level appears to shift with temperature at about one-half the rate of the shift in band gap energy.     

Type-II superlattice detectors for free space optics applications and higher operating temperature conditions

The utmost limit performance of interband cascade detectors optimized for the longwave range of infrared radiation is investigated in this work. Currently, materials from the III–V group are characterized by short carrier lifetimes limited by Shockley-Read-Hall generation and recombination processes. The maximum carrier lifetime values reported at 77 K for the type-II superlattices InAs/GaSb and InAs/InAsSb in a longwave range correspond to ～200 and ～400 ns. We estimated theoretical detectivity of interband cascade detectors assuming above carrier lifetimes and a value of ～1–50 μs reported for a well-known HgCdTe material. It has been shown that for room temperature the limit value of detctivity is of ～3–4×10¹⁰ cmHz^1/2/W for the optimized detector operating at the wavelength range ～10 μm could be reached.     

Photoconduction spectroscopy of p-type GaSb films

Excess carrier lifetimes (77 K) have been measured as function of the absorbed flux density in undoped p-type gallium antimonide films (GaSb/GaAs) using steady state photoconductivity measurements with the illumination wavelength of 1.1 μm. Using the results from Hall effect measurements along with the relations describing the lifetimes of the excess minority carriers in the bulk of the films and at the surface, the theoretical values of the effective excess carrier lifetime in the materials were also calculated. Discrepancies between the experimental and theoretical results were described using a two-layer model, by considering the variation in the charge distribution within the layer due to the presence of surface states, as well as the band offset between the layer and the substrate. Theoretical modeling of the experimental result yields values of different parameters such as band bending at the surface, minimum value of Shockley–Read–Hall lifetime and maximum value of the surface recombination velocity.     

Annealing of γ-ray irradiated lithium compensated p-type silicon

Abstract

Annealing behavior of electrical properties and photoluminescence spectra both at 77 °K in electron-irradiated melt-grown n-GaAs were investigated. Defects electrically active in the Hall mobility and carrier removal anneal through two stages centered at 250° and 460 °K. From the temperature dependence of carrier concentration the existence of a defect level located near 0.15 eV below the conduction band is supposed. Several emission bands are resolved at 1.51, 1.47, 1.415, 1.305 and ～1.2 eV in photoluminescence experiments. Electron irradiation (1.5–2.0 MeV) causes a remarkable decrease in emission intensity of 1.51 and ～1.2 eV bands. Recovery of emission intensity occurs remarkably when samples are annealed to 520 °K which would correspond to the 460 °K annealing stage for carrier concentration and Hall mobility. The 250 °K annealing stage is not observed in photoluminescence experiments. The 1.415 eV peak appears clearly after irradiation and grows remarkably with the 520 °K annealing, especially in Si-doped samples, resulting in large reverse annealing. This band is tentatively speculated to be a complex of Si on As site with As vacancy. Moreover, in samples doped with Te a new emission band at 1.305 eV (9500 Å) is observed after 470°–620 °K annealing.     

Influence of an ultrahigh -frequency electric field on the parameters of p-type indium antimonide

Using an ultrahigh-frequency, noncontact resonator method, the Influence of an electric field on the conductivity and the minority carrier lifetime in p-type InSb at 80K was studied. The conductivity of p-type InSb increased with increasing electric field; this effect was attributed to an increase in the carrier concentration as a result of impact (shock) iontzation, while the change taking place in the minority carrier lifetime was attributed to charge exchange in the recombination centers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 80–83, October, 1974.In conclusion, the authors are pleased to thank V. Vo Galavanov and N. S. Baryshev for useful discussions of the results, and V. S. Ivlevaya for providing samples.     

Surface photovoltage and internal photoemission at the anodized InSb surface

Surface photovoltage measurements have been made as a function of wavelength and temperature on a number of variously doped samples of n- and p-type InSb in the carrier concentration range of 8.9 × 10¹³ to 1.0 × 10¹⁸ cm^?3. The measurements were made using an MIS sandwich employing for the dielectric an anodically formed layer of In₂ O₃. Differential capacitance measurements have shown that, when cooled in the dark, the surface of the n-type material is near flat band whereas that of the p-type is depleted. Illumination with photons of energy in excess of ～ 1.5 eV leads to a shift of the surface potential to larger negative values presumably as a result of optical activation of electrons from fast interfacial surface states to slow states near the InSb surface. Internal photoemission measurements lend support to this model and suggest that, in the absence of any applied bias an internal field within the oxide causes the electrons excited from the semiconductor to move towards the metal. A theory for the surface photovoltage in the presence of a continuum of surface states is developed. It is concluded from theory, and supported by experiment, that surface trapping as well as recombination can exert a considerable influence on the photovoltaic response.     

Space-charge-limited currents and photoconductive properties of Tl2InGaSe4 layered crystals

The extrinsic electronic parameters of Tl₂InGaSe₄ layered crystals were investigated through measurement of the temperature-dependent dark conductivity, space-charge-limited currents and photoconductivity. Analysis of the dark conductivity reveals the existence of two extrinsic energy levels at 0.40 and 0.51 eV below the conduction band edge, which are dominant above and below 260 K, respectively. Current–voltage characteristics show that the one at 0.51 eV is a trapping energy level with a concentration of (4.8–7.7) × 10¹⁰ cm^?3. Photoconductivity measurements reveal the existence of another energy level located at 0.16 eV. In the studied temperature range, the photocurrent increases with increasing temperature. The dependence of the photoconductivity on the incident light intensity exhibits a linear recombination character near room temperature and a supralinear character as the temperature decreases. The change in recombination mechanism is attributed to an exchange in the behavior of sensitizing and recombination centres.     

Electroluminescence in CuGaSe2 single crystals

Electroluminescence has been observed in p-type CuGaSe₂ single crystals. At room temperature these crystals exhibit a resistivity of about 10^?2 Ω cm. The electrominescence has been obtained by minority carrier injection from an indium electrode. Two peaks have been identified in the emission spectrum whose energies are 1.53 and 1.59 eV, respectively. These peaks could be caused by the recombination of injected minority carriers in acceptor centers which are localized in the forbidden gap near the valence band.     

Temperaturabhängigkeit der Austrittsarbeit von Silizium

The temperature dependence of the work function of silicon was measured in ultra high vacuum between room temperature and 1000°K by means of the temperature dependent contact potential between the silicon surface and a metal reference with the Kelvin method. We have investigated both (111)-surfaces of p-type silicon, cleaned by heating in vacuum, and cleaved surfaces of different doping. For stable surfaces, temperature coefficients between 0 and +1·10^?4 eV/°K are found. Neither doping nor the transition of electrical conductivity from extrinsic to intrinsic has significant influence. This is due to the high density of surface states near the Fermi-energy. Freshly cleaved surfaces are unstable; when first heated up, an irreversible behaviour of the work function is observed, which gives some information concerning the surface states. From our measurements one can also roughly deduce the temperature dependence of the electron affinity. Finally, changes of the temperature dependence of the work function caused by contamination of the surface were investigated.     

Temperature-dependent optical properties of GaSe layered single crystals

Optical properties of GaSe single crystals have been investigated using temperature-dependent transmission and room temperature reflection measurements in the wavelength range of 380–1100 nm. The analysis of the absorption data at room temperature showed the existence of indirect transitions in the crystal with energy band gap of 1.98 eV. Temperature dependence of the transmission measurements revealed the shift of the absorption edge toward lower energy as temperature is increased from 10 to 280 K. The rate of change of the indirect band gap was found as γ = ?6.6 × 10^?4 eV/K from the analysis of experimental data under the light of theoretical relation giving the band gap energy as a function of temperature. The absolute zero value of the band gap energy and Debye temperature were calculated from the same analysis. The Wemple–DiDomenico single-effective-oscillator model applied to refractive index dispersion data was used to determine the oscillator energy, dispersion energy, oscillator strength and zero-frequency refractive index values.