Tellurium-implanted N+ layers in GaAs

Ion implantation of Te was investigated as a doping process for the fabrication of submicron n-type layers in GaAs. The implantation was performed with substrates held at 350°C. After implantation, a protective overcoat of AIN or Si₃N₄ was sputtered on the samples to prevent the GaAs from disassociating during anneal (900°C). The electrical characteristics of the n-type implants were then measured. Current-voltage and capacitance-voltage characteristics of implanted diodes indicated that the junctions were linearly graded and that there was no intrinsic layer present after anneal. Sheet resistivity and Hall effect measurements were used to determine the surface carrier concentration and effective mobility in the implanted layers. Ionized impurity profiles extending beyond the implanted junction depth were calculated by matching differential Hall effect data with junction capacitance-voltage data. A peak electron concentration of 7 × 10¹⁸ electrons/cm³ was observed. However, the profiles exhibited penetrating tails that resulted in junction depths being much deeper than the LSS range theory would predict.     

GaAs SAMP Device for Ku-Band Switching

Switchable attenuating medium propagation (SAMP) devices are coplanar transmission lines on an epitaxial semiconductor (GaAs) substrate. These transmission lines can be switched rapidly between states of high and low attenuation by controlling the width of a depletion layer under the center conductor. SAMP devices can easily be characterized by the use of transmission line theory. They are well suited for use in monolithic microwave integrated circuits (MMIC's). Experimental performance data and theoretical background will be presented.     

GaAs超高速模拟开关集成电路

本文首次报导了GaAs超高速模拟开关集成电路的设计、制备及主要结果。已制备出开启时间最好水平为0.7ns的实用开关集成电路是目前速度最快的模拟开关集成电路。     

Incoherent annealing of implanted layers in GaAs

Incoherent light from filament lamps focused by elliptical mirrors has been used to activate implanted layers in GaAs. 4 × 10¹⁴Si⁺cm^-2and 2 × 10¹⁴Zn⁺cm^-2implants were annealed with Si3N4deposited by CVD at 400°C providing a surface protective layer. By taking advantage of the focusing properties of elliptical mirrors, most of the emitted light could be concentrated onto the GaAs to give annealing times × 1 sec. Differential Hall measurements show peak carrier concentrations of 6.5 × 10¹⁸cm^-3and 50% activation for the n+ layers. The Zn implants were completely activated and doped to ∼ 2 × 10¹⁹cm^-3. These results, together with the short annealing times, suggest the present approach to be an attractive alternative to both laser and conventional thermal annealing.     

Electron transport in implant isolation GaAs layers

We report results of ac electrical characterisation of diode structures with Hg electrodes and an implant isolation layer formed on a n⁺GaAs substrate. The C–f and G–f characteristics at varying bias voltage between 0 and 10 V at room temperature were examined. The frequency of 50 mV measuring signal was changed from 100 Hz to 10 MHz. The implant isolation layers were performed by ion implantation of oxygen with 100 keV followed by 250 keV process on well conducting commercial GaAs substrate. Ion doses ranging from 10¹² to 5×10¹³ cm⁻² were used. The high frequency C–V characteristics showed that all tested implant isolation layers were fully depleted beginning from zero bias voltage. The G–f characteristics showed that ac conductance increases as a function of frequency and approximately follows ω^s dependence with s=0.6–0.9. These results are consistently interpreted as the result of the transport of injected carriers through the implant isolation layer via a hopping mechanism involving defects. Only in the samples with low level of defect density (low ion dose of 10¹² cm⁻²) for low frequency from 100 Hz to 5 kHz the high level conductance does not depend on frequency. This can be interpreted as the result of the transport of injected carriers through the extended states in conduction band.     

Photoluminescence of Si-doped GaAs epitaxial layers

The effect of arsenic pressure on the amphoteric behavior of Si during the growth of the Si-doped (100)-, (111)Ga-, and (111)As-oriented GaAs layers is studied by photoluminescence spectroscopy. The edge luminescence band is examined, and the concentration and the degree of compensation as functions of the arsenic pressure are determined. Nonstoichiometry defects in GaAs layers grown with a deficit and an excess of arsenic are studied. It is shown that the defects formed in the (111)Ga- and (111)As-oriented layers are different in nature.     

Photoelastic optical directional couplers in epitaxial GaAs layers

Photoelastic channel optical waveguides showing strong lateral confinement at ?=1.55 ?m have been fabricated by etching a narrow slot through a Au Schottky contact deposited on an n/n+ GaAs layer. Such structures allow electro-optic directional coupler switches of short coupling length (~2 mm) to be easily realised.     

Photoelastic channel optical waveguides in epitaxial GaAs layers

Photoelastic channel optical waveguides have been fabricated in GaAs epitaxial layers. These waveguides exhibit strong lateral confinement in a single region of their cross-section. They compare favourably with previously demonstrated integrated optical waveguide structures.     

Hubbard's sub-band conduction in Si poly-SiO2 transition layers

Conductivity and Hall coefficients were measured between 20 K and 380 K in boron-doped polysilicon films. The highly-doped samples were degenerate but unintentionally doped samples exhibited unusual behavior for polycrystalline film.To interpret the electrical properties of these samples we assumed the existence of a fine-grained non-degenerate transition layer near the Si poly-SiO₂ interface.Cross-sectional transmission electron microscopy and SIMS analysis confirmed the existence of this interface layer, which has a residual boron concentration resulting in conductivity with two activation energies, ε₁ at high temperatures and ε₂ at low temperatures in accordance with Hubbard's sub-band model.     

Observation of bias-dependent capture-emission processes in MBE-grown GaAs layers

The capture-emission process in a semiconductor sample was greatly affected by a varying electric field in DLTS analysis. The sample was an n-type GaAs layer grown on a 〈100〉-oriented seimi-insulating substrate by molecular beam epitaxy. An E_c − 0.5 eV electron trap level was found under lower bias voltage (−6 V) while both E_c − 0.40 eV and E_c − 0.50 eV traps were observed under higher bias voltage (−7.0 to −8.0 V). Emission rates have been measured that increased with increasing bias voltage from 0 V to −5 V and then decreased when biases were higher than −5 V. In the capacitance transient, when it revealed a delay, two levels, namely at −0.4 and −0.5 eV, appeared in the DLTS signals. However, the EL2 trap (E_c − 0.78 eV), found on another sample, revealed monotonically increasing emission with increasing bias.An explanation of these phenomena was proposed in light of the interaction of these two levels due to the electric field effect.     

Characterisation of Se implanted layers for GaAs FETs

Results on doping profile, uniformity of doping and mobility for Se implanted LEC grown semi-insulating GaAs substrates are presented as a function of Se ion energy and annealing temperature. SiO₂, RF sputtered Si₃N₄ and Ga₂O₃+Al are used as encapsulating layers. Surface effects (stress and damage) on doping efficiency of implanted Se ions are also included.     

Comprehensive investigation of trap-assisted conduction in ultra-thin SrTiO3 layers

The conduction in thin SrTiO₃ (STO) films has been investigated. Characterization of leakage current as a function of bias, temperature and film thickness indicates field enhanced hopping as the dominating conduction mechanism. The findings were confirmed by photo-conductivity measurements and agree well with simulation results.     

Role of substrate in electrical properties of GaAs implanted layers

The variation of implantation efficiency in different semi-insulating GaAs materials is shown to be correlated with he purity of the starting substrate, i.e. its Cr concentration and more especially its value of ND?NA (shallow levels). This last value appears to be a key parameter in the electrical properties of implanted layers.     

LSA operation of GaAs layers in large-scale tunable microwave circuits

It is shown that the attainment of LSA oscillations in epitaxial layers of GaAs does not rely on operation of the layers in small primary resonant circuits. Restrictions on circuit dimensions have thus been relaxed and LSA oscillations obtained in large scale microwave cavities. Layers of thickness 9-12.5 microns have been operated at frequencies from 26.5-40 GHz, the oscillations being tuned over this band by a conventional short-circuit plunger. The frequency of LSA oscillation is shown to be determined entirely by the natural circuit frequency. The tuning characteristics of the oscillations in various waveguide circuits are described and some general circuit features emerge which are of importance for a tunable LSA source. In particular it is noted that in some circuits a localized and therefore fixed frequency resonance occurs. It is also noted that LSA oscillations cannot occur if circuit Q is insufficiently high. The work has been carried out on a pulse basis to avoid thermal effects, and most of the experiments described have been carried out using unencapsulated devices. The maximum efficiency observed in these experiments was 4 percent.     

宽带GaAs MESFET开关模型

提出了一种 MESFET开关的模型——附加栅控开关模型 ,适用于 MMIC电路的设计 ,具有很好的宽带微波特性。在 0 .1～ 2 0 GHz频率范围内 ,器件测试值与模型模拟值吻合较好     

Microwave MESFET's fabricated in GaAs layers grown on SOS Substrates

Device-quality GaAs layers have been grown on silicon-on-sapphire (SOS) substrates by molecular beam epitaxy (MBE). Microwave MESFET's (gate length of ~0.8 µm) with transconductance of 140 mS/ mm,f_{max} = 20GHz, andf_{T} = 8.3GHz have been fabricated in these layers.     

Optoelectronic Microwave Switching via Laser-Induced Plasma Tapers in GaAs Microstrip Sections

This paper presents a new type of high-speed optoelectronic GaAs microstrip switch controlled by a pulse-operated laser diode via substrate-edge excitation. The exponential decay of photoconductivity across a longitudinal section of the microstrip forms a laser-induced electron-hole plasma wedge that works as a lossy tapered transmission line. The dynamics of carrier generation and recombination as well as the overall performance of the switch are quantitatively analyzed and optimized. This device is capable of switching with subnanosecond precision as well as with optical pule energies in the order of 1 µJ. Theoretical and experimental results were found to be in god agreement.