摘要:

The photoluminescence of Ge‐doped AlxGa1−xAs and Sn‐doped GaAs were investigated at 1.4 K. The ionization energy of Ge is strongly dependent on the Al composition in AlGaAs, and is in very poor agreement with the effective mass value. The ionization energy of Sn was found to be 110 meV in contrast with previously reported values. We also report a Sn acceptor bound excitation line at 1.507 eV in Sn‐doped GaAs, and a broad luminescence band peaking at ∼1.5 eV in Ge‐doped AlGaAs.

ISSN:0021-8979    

DOI:10.1063/1.335227

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The luminescence generated by hole injection from an aqueous electrolyte into GaAs and InP has been investigated. Solid‐state properties are responsible for the variations encountered in different samples and for most differences observed between photoluminescence and electroluminescence.

ISSN:0021-8979    

DOI:10.1063/1.335228

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

ZnSe:Mn dc thin‐film electroluminescent (EL) devices were prepared by a molecular beam growth method on glass substrates coated with transparent conductive oxide. We found that the EL properties were affected by the grade of the oxide. The EL properties were found to depend on the range of indium diffusion from the oxide to the ZnSe:Mn host layer. The effective thickness of the host layer was varied by the In diffusion. Based upon these results, we have proposed a new type of dc thin‐film EL cell, namely an Al/ZnSe:Mn/ZnSe:In/oxide structure. A ZnSe:In layer was prepared as a buffer layer that would improve the crystallinity of the ZnSe:Mn host layer.

ISSN:0021-8979    

DOI:10.1063/1.335229

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Irradiation of organic polymers by short pulses of far‐UV (e.g., 193 nm) laser light causes ablative photodecomposition (APD) of the material. This etching process occurs cleanly leaving behind a well‐defined pit. Longer wavelength (e.g., 532 nm) laser light also ablates material from a polymeric solid. However, this process is distinct from APD in that the sample near the pit is distorted and melted. Microscopic models are presented here for both the photochemical and thermal processes. The photochemical model predicts that well‐defined pits will be formed, that narrow angular distributions of the ablated material should be observed, and that the average perpendicular ejection velocity will be 1000–2000 m/s. The thermal model predicts melting or distortion of the solid and a broad angular distribution of the ejected material.

ISSN:0021-8979    

DOI:10.1063/1.335230

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The ion‐beam‐induced and subsequent thermal transformations at the Fe‐Si interface are studied by using the technique of interface‐sensitive conversion electron Mo¨ssbauer spectroscopy (CEMS). The samples used in these experiments have been prepared by depositing a thin (∼50‐A˚) layer of Fe57isotope (enriched to 95.45%) on a freshly cleaned surface of a (111) silicon crystal followed by a deposition of a 250‐A˚‐thick overlayer of natural iron containing only 2.2% of the Fe57isotope. A number of such composites have been bombarded with Xe+ions having an energy of 10 keV at an ion dose of ∼1–3×1016ions/cm2. The atomic mixing at the interface is confirmed by Rutherford backscattering (RBS) measurements and the average composition of the mixed layer is also determined. Using the CEMS technique, it is shown that the thin FeSi layer formed at the interface due to the deposition‐induced reaction grows upon ion bombardment, along with the incorporation of a large number of vacancies in the structure. It has also been shown that the internal magnetic field of the ion‐beam‐mixed alloy shows a broad distribution over a range of field values between 100 and 330 kOe with indications of certain preferences for local atomic arrangements and compositions. The ion‐beam‐mixed sample shows significant changes in the values of hyperfine interaction parameters subsequent to vacuum annealing treatment at 450 °C for 1 h, while precipitation of &agr;‐Fe and Fe3Si phases upon annealing at 700 °C. The as‐deposited sample exhibits distinctly different features as compared to those of the ion‐beam‐mixed sample, when subjected to thermal treatments. These thermal transformations in the as‐deposited as well as ion‐beam‐mixed samples have also been monitored by resistance annealing measurements, and the result of these studies agree well with those of CEMS measurements.

ISSN:0021-8979    

DOI:10.1063/1.335231

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Emission and absorption spectroscopic studies of a reactor used to grow germanium thin films by photodissociating GeH4at 248 nm with an excimer laser are described here. For every Ge or GeH (A→X) transition examined, the dependence of the emission line intensity on pump laser fluence was found to be quadratic, indicating that Ge and GeH have a common precursor which is itself produced by the simultaneous absorption of two 5‐eV photons. This conclusion is supported by the known photochemistry of SiH4and CH4in the ultraviolet and the laser wavelength and intensity thresholds for the growth of Ge films. The short (∼2 &mgr;s) lifetime of GeH2in the reactor suggests that theimmediateprecursor to Ge and GeH is the germyl radical, GeH3. The activation energy for Ge film growth in the temperature range 300≤T≤500 K has been measured to be 2.0±0.5 kcal/mole which suggests that the limiting mechanisms for the film growth rate are a gas‐phase reaction and surface desorption of residual gases rather than surface diffusion. Radiation trapping on several Ge emission lines and absorption measurements at 422.6 nm indicate that the steady‐state Ge number density in the reactor is ∼1012cm−3which is sufficient to account for the observed film growth rates. Spatial profiles of the atomic Ge and GeH emission from the reactor have been measured with a resolution of ∼100 &mgr;m.

ISSN:0021-8979    

DOI:10.1063/1.335232

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The quantitative analysis of carbon in liquid‐encapsulated Czochralski (LEC) GaAs crystals has been investigated using secondary ion mass spectrometry (SIMS). Localized vibrational mode (LVM) infrared absorption measurements are calibrated by SIMS results. A LVM absorption of 1 cm−2arisen from carbon was found to be produced by a carbon concentration of 9.5±2.9×1015atoms cm−3at room temperature. This carbon LVM optical cross section is 2.7 times larger than the value which had previously been reported. Carbon concentrations in LEC GaAs crystals are estimated to be 1–3×1015cm−3or lower.

ISSN:0021-8979    

DOI:10.1063/1.335498

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A silicon‐on‐sapphire lateral thin‐film bipolar junction transistor is unique in that recombination on the interface between the overlying silicon dioxide layer and the silicon semiconductor underneath must be taken into account. A simplified model of recombination is developed and then applied to determine the recombination currents in the bulk of the base of a bipolar junction transistor and in adjacent space‐charge regions. The expressions for these currents are used to modify the conventional Gummel–Poon model to include recombination on the top surface of a lateral bipolar junction transistor. In the modified form essential constants retain their original meanings.

ISSN:0021-8979    

DOI:10.1063/1.335233

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The minority carrier lifetime (&tgr;) in the base region ofn+‐psilicon solar cells has been measured in the temperature range ∼77–400 °K using the open‐circuit voltage decay technique. The injection level has been maintained constant in the entire temperature region. Experiment and theory agree in a small temperature region if &tgr;n0(minority carrier lifetime in heavily dopedpsilicon) is assumed to be temperature independent. However, an excellent fit between experimental and theoretical results is obtained if &tgr;n0is assumed to vary as exp[−(E&tgr;n0/kT)].

ISSN:0021-8979    

DOI:10.1063/1.335234

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Double heterostructure lasers were fabricated in which one of the laser facets was produced by a hybrid wet and reactive‐ion‐etching technique. This technique is suitable for GaAs/GaAlAs heterostructure lasers and utilizes the selectivity of the plasma in preferentially etching GaAs over GaAlAs. Lasers fabricated by this technique are compatible with optoelectronic integration and have threshold currents and quantum efficiency comparable to lasers with both mirrors formed by cleaving. The technique enables the use of relatively higher pressures of noncorrosive gases in the etch plasma resulting in smoother mirror surfaces and further eliminates the nonreproducibility inherent in the etching of GaAlAs layers.

ISSN:0021-8979    

DOI:10.1063/1.335235

出版商:AIP    

年代:1985

数据来源: AIP