In0.53Ga0.47As PIN光电探测器的温度特性分析

从理论和实验上分析了双异质结In0.53Ga0.47As PIN光电探测器在不同的反向偏置电压下暗电流在甚宽温度范围内的温度特性。结果表明：在反向偏置低压与高压段,产生一复合电流与隧道电流(缺陷隧道电流与带带间隧道电流)分别占主导地位,并呈现出相应的温度特性。还从理论与实验两方面探讨了噪声对探测器R0A的影响,结果表明：在低温段,产生一复合噪声起主要作用,在高温段,俄歇复合噪声起主要作用。     

高性能In0.53Ga0.47AsPIN光电探测器的研制

报道了采用GSMBE方法研制的In0.53Ga0.47As PIN光电探测器，器件结构中引入了宽禁带InP窗口层和聚酰亚胺钝化工艺，减小了暗电流，提高了器件性能。在反向偏压为5V时器件的暗电流为640pA，反向偏压为10V时测得器件的上升时间为37.2ps，下降时间为30.45ps，半高宽为43.9ps。对影响探测器暗电流的因素和提高响应速度的途径进行了讨论。     

Radiation damage of In0.53Ga0.47As photodiodes by high energy particles

The performance degradation of In_0.53Ga_0.47As p-i-n photodiodes, subjected to a 220-MeV carbon particle irradiation in the fluence range 10¹⁰ to 10¹³ cm^–2, is reported. It is shown that the increase of the dark current scales roughly with the displacement damage created in the n-type InGaAs region. The degradation of the photo-current, on the other hand, does not scale with the displacement damage, for all irradiations studied. Therefore, it is believed that the photo-current suffers from increased surface recombination, which is related to the ionization damage created in the passivation layer.     

In0.53Ga0.47As/InP(001)薄膜表面重构的研究

通过扫描隧道显微镜(STM)以及反射式高能电子衍射(RHEED)对在不同As4等效束流压强(As4BEP)下生长的In0.53 Ga0.47 As薄膜表面重构进行研究.研究发现在两种As4 BEP条件下,样品表面重构都以(4×3)/(n×3)为主,并存在c(6×4)、β2(2×4)以及α2(2×4)三种重构类型.和低As4 BEP条件相比,高As4 BEP条件下反射式高能电子衍射仪图像更加清晰,高分辨率的STM扫描图片也能够分辨出各种重构类型.对高分辨率的STM扫描图像进行进一步分析得到,随着As4 BEP的升高,β2(2×4)重构类型明显减少,这是由于高As4 BEP减少In偏析,从而抑制β2(2×4)重构的产生.     

Photoluminescence of heterostructures with highly strained GaAs quantum wells in Al0.48In0.52As and Ga0.47In0.53As layers

Heterostructures comprising highly strained GaAs quantum wells in Al_0.48In_0.52As and Ga_0.47In_0.53As layers have been grown by the metalorganic chemical vapor deposition method on InP(100) substrates. The photoluminescence spectra of these structures have been studied, and it is established that GaAs quantum wells form type-I heterojunctions with Al_0.48In_0.52As layers and type-II heterojunctions with Ga_0.47In_0.53As layers.     

High field transport characteristics of minority electrons in p-In0.53Ga0.47As

Measurements of the static current-voltage characteristics of photoexcited minority electrons in p-In_0.53Ga_0.47As are reported. Photoluminescence measurements are also presented. These results are discussed in terms of the theory for high field photoconductivity and the recently reported velocity-field characteristics for minority electrons in In_0.53Ga_0.47As.     

Structural Control of Rashba Spin–Orbit Coupling in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As Quantum Wells

We investigated the correlation between the Rashba spin–orbit coefficient α and potential shape of the quantum wells (QW), where α values are experimentally deduced from the weak antilocalization analysis. We studied the gate I–V properties of the QW samples and have obtained results consistent with the potential shapes predicted for these QWs.     

Schottky barrier height enhancement on n-In0.53Ga0.47As by (NH4)2S x surface treatment

(NH₄)₂S _x Surface treatment was found to increase the barrier height (_Bn) for Au/In_0.53Ga_0.47As Schottky junctions from 0.26 eV to 0.58 eV at 300 K as determined from Richardson plots. The ideality factorn thus decreased from 2.7 to 1.6 and the reverse saturation current densityJ ₀ from 9.4 Acm^–2 to 3.4×10^–5A cm^–2. The values of the effective Richardson constant were also evaluated. The chemical state of In_0.53Ga_0.47As surfaces before and after (NH₄)₂S _x modification, examined by X-ray photoelectron spectroscopy (XPS), indicated bond formation of S with In, Ga and As.     

Electrical characterization of deep levels existing in fully implanted and rapid thermal annealed p+n InP junctions

In this paper, the deep levels existing in fully implanted and rapid thermal annealed p⁺n junctions obtained by Mg/Si or Mg/P/Si implantations on nominally undoped n-type InP substrates were detected and characterized by the correlation of two electrical techniques: deep level transient spectroscopy (DLTS) and capacitance–voltage transient technique (CVTT). Two ion implantation-induced deep levels (at 0.25 and 0.27 eV below the conduction band) were detected by DLTS. Several characteristics of these traps were derived from CVTT measurements, paying special attention to their physical nature.     

Electrical characterization of shallow cobalt-silicided junctions

The impact of the thickness of the cobalt-silicide layer on the electrical diode characteristics will be reported, with particular emphasis on the current-voltage (I-V characteristics, the surface and bulk carrier recombination lifetime and the low-frequency noise. It is shown that for thicker silicides the generation-recombination of holes in the top n⁺-layer is enhanced, giving rise to a higher diffusion current, an increase in the noise and a larger surface recombination velocity. It is believed that these parameters are closely linked, as the underlying physical phenomenon is the minority carrier recombination. In addition, it is shown by transmission electron microscopy that the silicide-silicon interface roughness is increased for larger cobalt thickness, which may explain some of the observations.     

Functional properties of microstrip Si detector structures with implanted p-n junctions

The basic properties of microstrip Si detector structures with p-n junctions and the technological procedures for their production are described. Some results of manufacturing strip detectors with 200 μm and 20 μm strips are presented.     

InAs quantum dots capped by GaAs,In0.4Ga0.6As dots,and In0.2Ga0.8As well

We have fabricated and characterized three types of InAs quantum dots (QDs) with different InxGa1-xAs capping layers. Post-growth atomic force microscopy measurements show that the In0.2Ga0.8As/InAs structure has a smooth surface (dot-in-well structure), whereas the In0.4Ga0.6As/InAs structure revealed large QDs with a density similar to that underneath InAs QDs on GaAs (dot-in-dot). With increasing In mole fraction of the capping layer and increasing In0.4Ga0.6As thickness, the energy position of the room-temperature photoluminescence (PL) peak is red-shifted. The quantum dot-in-dot structure emits stronger room-temperature PL than does the quantum dot-in-well structure. With a spatially distributed strain in the InAs quantum dot, we have solved the three-dimensional Schr?dinger equation by the Green's function theory for the eigenvalues and eigen wave functions. It is concluded that the ground state increases its wave function penetration into the low-barrier InxGa1-xAs capping layer so that its energy position is red-shifted. The reduced PL peak intensity of the dot-in-well (compared with GaAs covered dots) is due to the reduced overlapping between the ground state and the extended states above the GaAs barrier. The overlapping reduction in the dot-in-dot is over compensated for by the reduced relaxation energy (full width at half-maximum), indicating the importance of the sample quality in determining the PL intensity.     

Electrical Properties and Ferromagnetism in (Ga,Cr)As

MBE-grown (Ga,Cr)As has interesting electric and magnetic properties. Ga_1–x Cr _x As with x = 0.1 exhibits short-range ferromagnetic behavior at low temperatures. This is manifest in several anomalous properties: magnetization does not scale with B/T; fitting M(B) requires a model of distributed magnetic cluster or polarons; and inverse susceptibility is nonliner in T (non-Curie–Weiss) at low fields. At room temperature, the conductivity is activated and Hall measurements yield a hole concentration of 10²⁰ cm^–3, indicating that chromium acts as an acceptor similar to Mn in GaAs. For decreasing temperature, the conductivity decreases by eight orders of magnitude and follows exp(1/T ^1/2).     

Alloying (In,Mn)As and (Ga,Mn)As: Ferromagnetic (In,Ga,Mn)As Lattice-Matched to InP

An effect of alloying two ferromagnetic semiconductors (In,Mn)As and (Ga,Mn)As on the ferromagnetic properties of resultant (In,Ga,Mn)As alloys is reported. For conditions close to lattice-matching to InP substrates, y = 0.53 in (In _y Ga_1–y )_1–x Mn _x As, ferromagnetism up to Curie temperatures T _C = 100–110 K could be achieved for a Mn composition x = 0.13. Trends in the Curie temperature in (In,Ga,Mn)As are compared with (Ga,Mn)As and (In,Mn)As as a function of Mn content. Hole concentrations determined from magnetotransport, taking into account the anomalous Hall contribution to Hall resistance, gives p/Mn = 0.03 ratio to Mn composition in metallic case for x = 0.13. We mention the possible role of chemical ordering (short range) of Mn impurity atoms on hole concentration and, consequently, for the ferromagnetic properties.     

Electrical characterization of deep levels in N and P 6H-SiC Schottky diodes

Excess current at low forward bias is observed for large-area Ni Schottky diodes on n- and p-type 6H-SiC. Random telegraph signal (RTS) measurements, carried out on these defective devices, show discrete time switching of the current. The trap signatures (E_a=0.35eV>, =1.17×10^-18cm² for n-type, E_a=0.43eV, =1.8×10^-20cm² for p-type) extracted from deep level transient spectroscopy (DLTS) measurement are very close to those obtained from RTS. This strong correlation between the two different techniques is attributed to the presence of an extended defect which presents different charge states (i.e. an extended defect decorated by punctual traps). This assumption is reinforced by the DLTS measurements as a function of the filling time and as a function of the field.     

Electrical Electron Spin Injection with a p+-(Ga,Mn)As/n+-GaAs Tunnel Junction

We demonstrate electrical electron spin injection in a p⁺-(Ga,Mn)As/n⁺-GaAs tunnel junction with an n-GaAs/(In,Ga)As/p-GaAs light emitting diode (LED). By applying a reverse bias to the p⁺-(Ga,Mn)As/n⁺-GaAs junction (forward bias to the LED), we observed clear hysteresis in electroluminescence (EL) polarization. The magnitude of the EL polarization, which does not depend critically on the spacer layer thickness up to 800 nm, is found to be about five times greater than that of the hole spin injection.