Molecular beam epitaxial growth of green light emitting diodes on ZnSe wafers

We have performed a preliminary investigation into the use of ZnSe bulk crystals fabricated by Sumitomo Electric Industries, Ltd. as substrates for the epitaxial1 deposition of ZnSe-based materials and light emitting devices. A low temperature (<380 °C)in- situ cleaning process has been developed for the (100) oriented ZnSe wafers involving the use of a remotely generated atomic hydrogen beam. The process produces a (1 × 1) atomically smooth ZnSe surface which is highly suitable for epitaxy. Hall-effect measurements performed on nitrogen-doped ptype ZnSe/S.I. ZnSe epilayers have revealed free-hole concentrations in the homoepitaxial material as high as 2.1 × 10¹⁷cm⁻³, so far, with room temperature and 77Khole mobility values of 20 and 100 cm²V _su−1 ^ins/su−1 , respectively. Finally, green light emitting diodes have been grown on the ZnSe wafers having Cd_0.2Zn_0.8Se/ ZnSe multiple quantum well active regions which have exhibited electroluminescence peak linewidths around 9.9 nm at room temperature.     

方兴未艾的二极管泵浦的激光晶体材料

简要叙述了半导体激光器现存的一些问题和二极管泵浦固体激光器的特点,评述二极管泵浦激光晶体材料的最新进展。     

Multi-layer epitaxially grown silicon impatt diodes at millimeter-wave frequencies

Complementary (N⁺PP⁺) and double-drift (N⁺NPP⁺) silicon IMPATT diodes were prepared and investigated as oscillators in the millimeter-wave frequency region of 50 to 70 GHz. All the diodes were fabricated from multi-layer epitaxially grown silicon structures. A maximum CW output power level of 198 mW at 62.9 GHz and a maximum conversion efficiency of 7.3% have been measured for the complementary diodes. The double-drift IMPATT diodes have a maximum CW output power of 400 mW at 56.3 GHz and a maximum conversion efficiency of 8.5%.     

Characteristics of a GaN-based Gunn diode for THz signal generation

A generalized large-signal computer simulation program for a Gunn oscillator has been developed.The properties of a Gunn diode oscillator based on the widely explored GaN,are investigated using the dev...     

Fabrication of self-aligned graded junction termination extensions with applications to 4H-SiC P-N diodes

The properties of SiC make this wide band-gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices, such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc., all of which require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power-handling capabilities. In this paper, we describe a technique for fabricating a graded junction termination extension (GJTE) that is effective and self-aligned, a feature that simplifies the implantation process during fabrication and, therefore, has the potential to reduce production costs. Implanted anode p-n diodes fabricated using this technique on 10-μm thick n⁻ epitaxial layer had a maximum breakdown voltage of 1830 V. This was comparable to the ideal parallel-plane breakdown of 1900 V predicted by numerical simulation.     

Molecular beam epitaxy growth of high-quality arsenic-doped HgCdTe

We have initiated a joint effort to better elucidate the fundamental mechanisms underlying As-doping in molecular beam epitaxy (MBE)-grown HgCdTe. We have greatly increased the As incorporation rate by using an As cracker cell. With a cracker temperature of 700°C, As incorporation as high as 4×10²⁰ cm⁻³ has been achieved by using an As-reservoir temperature of only 175°C. This allows the growth of highly doped layers with high quality as measured by low dislocation density. Annealing experiments show higher As-activation efficiency with higher anneal temperatures for longer time and higher Hg overpressures. Data are presented for layers with a wide range of doping levels and for layer composition from 0.2 to 0.6.     

Planar n-on-p ion milled mid-wavelength and long-wavelength infrared diodes on molecular beam epitaxy vacancy-doped CdHgTe on CdZnTe

Planar mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) photodiodes were fabricated by ion milling molecular beam epitaxy (MBE) Cd_xHg_1−xTe (CMT) layers with and without compositional grading in the layer. Linear arrays with 32 and 64 diodes, as well as test diodes of varying size, were fabricated. Good quantum efficiencies were measured, and MWIR diodes, with cutoff wavelength λ_CO=4.5 μm, had zero-bias resistance-area values (R₀A) in excess of 1×10⁷ Ωcm², whereas LWIR diodes with λ_CO=8.9−9.3 μm had R₀A=3×10² Ωcm² at 77 K. Comparison between a limited number of layers indicates that in layers with a gradient the RA values are a factor of ∼10 larger, and possibly more uniform, than in layers without a gradient.     

Lasing properties of PbSnTe/PbTe double hetero mid-infrared laser diodes grown by temperature difference method under controlled vapor pressure liquid-phase epitaxy

PbSnTe/PbTe double hetero-diode structures were grown by temperature difference method under controlled vapor pressure (TDM–CVP) liquid-phase epitaxy (LPE). These laser diode (LD) structures were of the PbTe (Bi)/Pb_1−xSn_xTe/PbTe (undoped substrate) double hetero (DH) type. The peak shift of the wavelength emitted by the fabricated diodes was recorded and it was found that they successfully lased from 15 K to over 77 K (liquid nitrogen temperature) at a slightly lower threshold current density than standard LPEs fabricated via the slow-cooling method. In addition, the lasing peak wavelength was longer than spontaneous emissions. The laser spectra of diodes with varying Sn concentrations (x) in the active layer were observed, and their intensities were recorded as a function of the wavelength. Very sharp lasing spectra were obtained between 6.5 μm and 9.4 μm (x=0–0.11), clarifying that the stoichiometry control possible with TDM–CVP is suitable for fabricating optical devices. In addition, it was demonstrated that TDM–CVP is appropriate for fabricating infrared optical devices constructed from Pb_xSn_1−xTe systems.     

pn-Junction photodiode based on GaN grown on Si (111) by plasma-assisted molecular beam epitaxy

The growth and characterization of pn-junction photodiode based on GaN grown on Si (111) by RF-plasma assisted molecular beam epitaxy (MBE) are described. The structural and optical properties of samples were studied by HR-XRD and Fourier FTIR spectroscopy, respectively. For IR reflectance analysis, GaN-like and AlN-like E₂ TO optical modes have been detected. By using the thermal evaporator, Ni/Ag and Al contacts were evaporated at the front and back of samples. The application of thermal annealing treatment in oxygen ambient has been shown to significantly reduce the dark current of GaN pn-junction photodiode. The electrical characteristics of all samples were conducted using Keithley's I–V measurement system. Under 460-nm wavelength, at bias voltages of 0.5, 1, and 2 V, the photocurrents rise and decay times were investigated.     

Analysis of defect-assisted tunneling based on low frequency noise measurements of resonant tunnel diodes

An experimental apparatus and procedure using noise measurement techniques have been developed in order to identify conduction mechanisms in RTDs due to defect assisted tunneling. The theory of noise measurements is discussed as the basis for the appropriate modelling of RTD noise data. The activation energies and capture cross-sections have been determined in a typical RTD for each of three distinct trap levels. A conjecture is made as to the physical location of the traps. This interpretation yields qualitative behavior consistent with the known bias and temperature dependence of the experimental results.     

Effects of layer design on the performance of InAs/AlSb/GaSb resonant interband tunneling diodes on GaAs substrates

The room temperature current-voltage characteristics of InAs/AlSb/GaSb resonant interband tunneling diodes (RITDs), grown by chemical beam epitaxy on GaAs substrates, are reported as a function of the InAs buffer layer thickness and different interface configurations. The peak-to-valley current ratio (PVCR) improved from 1 to 12 as the buffer thickness was increased from 0 to 500 nm and the density of dislocations caused by the lattice mismatch of ∼7% decreased. No significant improvement was seen for a buffer thickness beyond 500 nm. Dislocation-free RITDs, grown lattice-matched on InAs substrates, show PVCRs of approximately 16. The InAs/AlSb Interfaces in these structures can be either InSb-like or AlAs-like and the interface can have a very strong effect on the diode performance. Unlike the case in InAs/AlSb field effect transistor structures, an AlAs-like interface results in better PVCRs in the diodes. Details of the results of this study are presented.     

The scanning tunneling microscopy and spectroscopy of GaSb1-xBix films of a few-nanometer thickness grown by molecular beam epitaxy

The ultrahigh vacuum scanning tunneling microscope (STM) was used to characterize the GaSb1-xBix films of a few nanometers thickness grown by the molecular beam epitaxy (MBE) on the GaSb buffer layer of 100 nm with the GaSb (100) sub-strates.The thickness of the GaSb1-xBix layers of the samples are 5 and 10 nm,respectively.For comparison,the GaSb buffer was also characterized and its STM image displays terraces whose surfaces are basically atomically flat and their roughness is generally less than 1 monolayer (ML).The surface of 5 nm GaSb1-xBix film reserves the same terraced morphology as the buffer layer.In contrast,the morphology of the 10 nm GaSb1-xBix film changes to the mound-like island structures with a height of a few MLs.The result implies the growth mode transition from the two-dimensional mode as displayed by the 5 nm film to the Stranski-Krastinov mode as displayed by the 10 nm film.The statistical analysis with the scanning tunneling spectroscopy (STS)measurements indicates that both the incorporation and the inhomogeneity of Bi atoms increase with the thickness of the GaSb1-xBix layer.     

AlGaInAs/InP strained-layer quantum well lasers at 1.3 µm grown by solid source molecular beam epitaxy

Al_xGa_yIn_1−x−yAs/InP strained-layer multiple-quantum-well lasers emitting at 1.3 μm have been grown by solid source molecular beam epitaxy, and the performance characteristics have been studied. The lasers contain 4, 5, or 6 compressively strained quantum wells in the active region. They exhibit low transparency current densities, high gain coefficients, and high characteristic temperatures compared to conventional GaInAsP/InP quantum well lasers. The results show that desired lasing features can be achieved with relatively simple layer structures if the doping profiles and waveguide structures are properly designed and the material is grown to high structural perfection.     

Molecular beam epitaxy growth of HgCdTe on Ge for third-generation infrared detectors

The Leti-Lir has studied II–VI compounds for infrared (IR) detection for more than 20 years. The need to reduce the production cost of IR focal plane arrays (FPAs) sparked the development of heteroepitaxy on large-area substrates. Germanium has been chosen as the heterosubstrate for the third generation of IR detectors. First, we report on the progress achieved in HgCdTe growth on 3-in. and 4-in. (211)B CdTe/Ge. Then, we discuss the choice of a new machine for larger size and better homogeneity. Finally, we present the latest results on third-generation IR multicolor and megapixel devices. First-time results regarding a middle wavelength infrared (MWIR) dual-band FPA, with a reduced pitch of 25 μm, and a MWIR 1,280×1,024 FPA will be shown. Both detectors are based on molecular beam epitaxy (MBE)-grown HgCdTe on Ge. The results shown validate the choice of Ge as the substrate for third-generation detectors.     

Space-charge effects and ac response of resonant tunneling double-barrier diodes

We analyse theoretically the small-signal ac response of a resonant tunneling double-barrier semiconductor diode using the sequential tunneling approach. Electrostatic feedback effects due to space charge buildup in the quantum well are included in the analysis. The results are expressed in terms of an equivalent circuit which is used to interpret measurements of the capacitance of an asymmetric double-barrier structure at low frequencies (< 1 MHz). The frequency dependence of the real and imaginary parts of the impedance at microwave frequencies are also discussed.     

Structural, electrical and magnetic characterizations of Ni/Cu/p-Si Schottky diodes prepared by liquid phase epitaxy

In this paper, we have investigated the structural, electrical and magnetic characterizations of Ni/Cu/p-Si Schottky diode prepared by liquid phase epitaxy (LPE). Current density-voltage (J-V), capacitance-voltage (C-V) and capacitance-frequency (C-f) measurements were performed to determine the conduction mechanisms as well as extracting the important diode parameters. Rectifying properties were obtained, which definitely of the Schottky diode type. At low voltages, (0 < V ? 0.4 V), current density in the forward direction was found to obey the diode equation, while for higher voltages, (0.5 < V ? 1.5 V), conduction was dominated by a space-charge-limited conduction (SCLC) mechanism. Analysis of the experimental data under reverse bias suggests a transition from electrode-limited to a bulk-limited conduction process for lower and higher applied voltages, respectively. Diode parameters such as, the built-in potential, V_b, the carrier concentration, N, the width of the depletion layer, W, of the Ni/Cu/p-Si Schottky diode were obtained from the C-V measurements at high frequency (1 MHz). The capacitance-frequency measurements showed that the values of capacitance were highly frequency dependent at low frequency region but independent at high frequencies. The Ni/Cu/p-Si Schottky diode showed magnetic properties due to the effect of Ni in the heterostructure.     

采用解析法估算弯曲波导超辐射发光二极管的光学损耗

器件弯曲区域的光学损耗对弯曲波导超辐射发光二极管(SLD)性能有着重要影响。对于器件制备和性能优化来说,若能对弯曲损耗作出估算,将大有裨益。在本论文中,我们推导出一个解析公式,可用于拟合器件P-I曲线而得到弯曲损耗系数。该公式已成功应用于对仿真P-I曲线损耗系数的估算(该P-I曲线通过一个复杂的量子点器件模型仿真得到),我们期待这一方法对估算实际器件损耗亦有效用。     

Molecular beam epitaxy growth of InGaSb/AlGaAsSb strained quantum well diode lasers

2μm InGaSb/AlGaAsSb strained quantum wells and a tellurium-doped GaSb buffer layer were grown by molecular beam epitaxy（MBE）.The growth parameters of strained quantum wells were optimized by AFM, XRD and PL at 77 K.The optimal growth temperature of quantum wells is 440℃.The PL peak wavelength of quantum wells at 300 K is 1.98μm,and the FWHM is 115 nm.Tellurium-doped GaSb buffer layers were optimized by Hall measurement.The optimal doping concentration is 1.127×10¹⁸ cm^-3 and the resistivity is 5.295×10^-3Ω·cm.     

2μm InGaSb/AlGaAsSb应变量子阱激光器的MBE生长研究

摘要：对InGaSb/AlGaAsSb应变量子阱和GaSb接触层掺Te的MBE生长进行了研究。通过原子力显微镜(AFM)、X射线衍射(XRD)设备、光致发光谱(PL)测试,对应变量子阱的生长参数进行了优化。量子阱室温PL测试,发光波长为1.98 μm,半峰宽为115nm。通过Hall测试优化了GaSb外延掺Te的生长参数,最优的掺杂浓度为1.1271018 cm-3,电阻率为5.29510-3Ω?cm。     

Molecular beam epitaxial growth and characterization of lead telluride for laser diodes

The characteristics of PbTe films grown by molecular beam epitaxy (MBE) have been investigated. These films were grown on (100) oriented Tl-doped PbTe substrates under UHV conditions (~5×l0⁻⁹ Torr during deposition). Substrate surface contamination levels were studied with Auger electron spectroscopy. Oxygen, the dominant impurity observed, is rapidly thermally desorbed from PbTe, but is stable on Pb_1−xSn_xTe up to at least 410°C. Carrier concentration and mobility were measured with the Van der Pauw technique. The electron mobility increased strongly with increasing film thickness, varying from 4,000 to 14,000 cm²/volt-sec as the thickness increased from 2.0 to 7.3 μn. The film surface also became smoother with increasing film thickness. These results suggest the need for a buffer layer in a laser structure. Lasers grown with 6 μm thick buffer layers have exhibited extremely low threshold current densities (40 A/cm² at 13 K) and very high junction resistancearea products at zero-bias (0.7 Ω−cm² at 77 K), indicative of very high junction quality.