摘要:

Results are presented on the use of metalorganic chemical‐vapor deposition (CVD)‐grown InGaP lattice matched to GaAs as part of a capping scheme to protect ann+GaAs epilayer during high‐temperature annealing. Such an epilayer structure is important for heterostructure metal‐semiconductor field‐effect transistors (HMESFETs). It is shown that a surface InGaP layer is more effective than undoped GaAs in preventing conductivity degradation and Si diffusion for ann+GaAs epilayer during high‐temperature annealing under plasma‐enhanced CVD SiO2capped condition. In addition, the mechanism of the protective effect is discussed. The results point to the potential applicability of the InGaP for protectingn+GaAs channel epilayers under the gates of HMESFETs during annealing after ion implantation for source/drain ohmic contact or device isolation. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360210

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The effects of electron–electron interaction on the electronic structure of a three‐dimensional model quantum box are studied. The potential in the lateral plane of the quantum box is taken to be a two‐dimensional harmonic potential, and an infinite quantum‐well potential is used to represent the confinement in the vertical direction. Three‐dimensional two‐electron wave functions are constructed by the configuration interaction technique. Exchange and correlation are found to affect the electronic structure strongly. The effect of the finite thickness of the quantum box on the electronic structure is examined. It is shown that the electron–electron interaction can induce interesting polarization effects not only in the lateral plane but also in the vertical direction of the quantum box. Numerical results based on GaAs material parameters are presented. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360211

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The temperature dependence of threshold current between 130 and 310 K of 1.65 &mgr;m In0.53Ga0.47As–InP bulk lasers grown by chemical beam epitaxy has been measured. Comparison with a calculation of the spontaneous recombination current at threshold allows one to determine the proportion of current loss over this temperature range. It is found that the loss can be described using an Auger recombination component of the formRauger=C’n3 exp(−Ea/kBT) wherenis the carrier population density in the undoped active region. The activation energyEais found to be 39±5 meV which is in excellent agreement with the theoretical value for the conduction to heavy hole band/split‐off to heavy hole band Auger process. The values obtained for the Auger coefficientCover the temperature range are in close agreement with published values obtained by time resolved photoluminescence. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360212

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A general method for processing deep level transient spectroscopy (DLTS) data is presented. It is shown that the theoretical model is a two‐dimensional Fredholm equation of the first kind with a four‐dimensional integral kernel. The method is based on the numerical solving of the inverse ill‐posed problem of the theoretical model via regularization algorithms. Starting from a two‐dimensionalC(T,t) surface one can obtain the correspondingC0(E,&sgr;) surface, i.e., the continuous distribution equivalent to the deep levels concentrations for a given sample in both energy and cross‐section coordinates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360213

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The characteristics of Si‐doped In0.52Al0.48As layers as a function of silicon doping ranging from 1×1017to 4×1018cm−3are analyzed by low‐temperature photoluminescence (PL), Raman spectroscopy, and Hall effect measurements. When the sample temperature is increased from 4 K, the PL peak energy exhibits an inverted S‐shaped dependence which is characteristic of carrier localization. This effect was more prominent at lower doping levels, but weakened at high doping levels due to a possible reduction in the donor binding energy. The peak energy variation at temperatures higher than ≊100 K follows the usual band‐edge variation with temperature, suggesting that the PL arises from band‐to‐band transitions. While the PL linewidth of the undoped and moderately doped samples decreases and then increases with temperature, a near‐monotonic increase in the linewidth due to thermal broadening was observed in highly doped samples. Supported by observations of a reduction in both the AlAs‐like and InAs‐like longitudinal‐optic (LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased, the PL intensity also showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous materials. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360214

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

High quality silicon dioxide films have been produced using a direct plasma‐enhanced chemical vapour deposition process with silane, nitrous oxide and helium that leaves a nitrided layer at the Si‐SiO2interface. X‐ray photoelectron spectroscopy coupled with etch‐back of the films has shown that the interface nitrogen is incorporated by nitridation of the silicon surface. Fowler–Nordheim injection measurements on thin films annealed after deposition for 1 minute at 950 °C show that the neutral‐trap generation and interface state generation rates are comparable to that of thermal oxide if a proper deposition power is chosen. The data is consistent with an interpretation in which fast donor states, notPbcentres, account for almost all of the increase in the charge trapped at the interface. Too high deposition powers lead to excessive nitrogen and higher interface state generation rates. It is proposed that improved performance under hot‐electron stress could be obtained by using an optimal deposition power to obtain an optimal nitrogen concentration followed by annealing in oxygen. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360762

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new model for the semi‐insulating polycrystalline silicon (SIPOS)‐silicon interface is proposed. The model explains the behaviour of the capacitance‐voltage characteristics of a metal‐ SIPOS‐silicon structure at low temperatures. A theoretical capacitance versus voltage (C–V) relationship has been calculated for low temperatures and fitted to measured data with very good agreement. The interface state density at the SIPOS–silicon interface has also been calculated using Terman’s method. We demonstrate that when determining the energy distributions of interface states between SIPOS and silicon by usingC–Vtechnique, thermal equilibrium between the interface and the silicon bulk has to be maintained by making the measurement at low temperature. Measurement at room temperature normally gives too low values of the interface state density, Dit. Ditvalues of approximately 1013cm−2eV−1were found for the SIPOS‐silicon interface with 25 at. % oxygen concentration. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360215

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The results of a detailed tight‐binding calculation of the electronic structure and optical properties of (ZnSe)n/(Ge2)m(110) superlattices are presented for a wide range ofn,m≤20. It is found that the fundamental energy gap increases with decreasing superlattice period due to spatial quantum confinement effects. For all reasonable values (ranging from 0.2 to 2.0 eV) of the valence band discontinuity used in the calculation, no interface states are found in the thermal gap of the (ZnSe)n/(Ge2)m(110) (n,m≤20) system. An indirect–direct band gap transition is found to be driven by increasing valence band offset. The optical properties of the superlattices are investigated by calculating the absorption coefficient. The results are analyzed according to the calculated electronic structure and compared with those of the corresponding bulk materials. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360216

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

There has been controversy concerning the energy gap of the cubic (zinc‐blende) form of the wide‐gap semiconductor GaN. Measurements are reported of the band gaps of both hexagonal (wurtzite) and cubic thin films deposited by a modified molecular‐beam‐epitaxy process on (001) GaAs and GaP substrates. The important difference from conventional MBE lies in the method of supplying nitrogen to the growing film. Here a rf nitrogen plasma source operating at 13 MHz is used. The structure of the films was monitored by x‐ray diffraction and controlled by the addition of an As beam which results in growth of the cubic form—otherwise films grow with the hexagonal structure. The band gaps were measured at room temperature by optical reflectivity, as evidenced by the sharp reduction in interference oscillations as the photon energy approached the band edge, and confirmed by the observation of band‐edge photoluminescence. The results can be summarized asEg=3.42±0.02 eV for the hexagonal and 3.22±0.02 eV for the cubic form. The observation of films containing mixed hexagonal and cubic phases, which may have led to earlier errors in band‐gap measurements, is also reported. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360217

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electron‐phonon coupling factor controls the heat transfer between electrons and lattice when thin metal films are heated by laser pulses with duration of order of femtoseconds. An inverse analysis is used to estimate this factor from transient measurements of the normalized variation of reflectivity and transmissivity of the metal film. The sensitivity coefficients are examined in order to determine the optimum time interval for the measurements. Results obtained with simulated measurements containing random errors show that the inverse analysis provides accurate estimates for the electron‐phonon coupling factor. A statistical analysis is performed for the evaluation of the confidence interval for the estimates. Actual experimental data of reflectivity and transmissivity available in the literature are used to estimate the electron‐phonon coupling factor for films of gold and copper. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360218

出版商:AIP    

年代:1995

数据来源: AIP