摘要:

The total oxygen content of a number of doped and undoped GaP crystals grown by the liquid encapsulated Czochralski technique has been determined using 10‐MeV He3beams. The level of oxygen ranges from 2 × 107to 5 × 1017atoms/cm3for the undoped ingots. Oxygen concentrations at the tail ends of the crystals were approximately twice those at the seed ends of the same crystals. A slight increase in oxygen concentration was also found toward the center region of a circular slice of the crystal. Ga2O3‐doped crystals contained up to five times more oxygen([inverted lazy s]2×1018)than undoped crystals. The systematic increase of the total oxygen solubility as a function of the concentration of Ga2O3added for the growth was also investigated. These results were then compared with total oxygen incorporated in crystals grown by vapor‐phase epitaxy.

ISSN:0021-8979    

DOI:10.1063/1.1662967

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Heterodiodes have been prepared by the growth of epitaxialn‐type CdS films from the component vapors onp‐type CuGaS2substrates. In dc operation at 77°K, green light is emitted with an external quantum efficiency of 0.1%. For pulsed operation at room temperature, the efficiency is[inverted lazy s]0.001%. The near‐band‐gap radiation results from electron injection into a semi‐insulating CuGaS2region near the CdS/CuGaS2interface. This region also controls the forward current of the diodes.

ISSN:0021-8979    

DOI:10.1063/1.1662968

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The depth distribution of phosphorus in silicon dioxide formed by reacting phosphine and silane with oxygen at 480°C, has been measured with Auger spectroscopy using (i) ramp‐etched silicon dioxide films and (ii)in situion milling. Quantitative Auger analysis showed the phosphorus concentration to be 0.5 at.% throughout most of the oxide. However, when grown directly on silicon, a phosphorusrich oxide, [sine wave] 30 Å thick and containing > 3 at.% phosphorus, was first deposited, followed by a phosphorus‐depleted region, [sine wave] 150 Å thick; both regions formed within the first minute of deposition and probably resulted from a rapid initial reaction of phosphine with the silicon surface. Neither region is formed when the doped oxide is deposited on silicon dioxide, and undoped oxides < 200 Å thick were successfully used to eliminate the phosphorus‐rich layer. There was negligible diffusion(≲100  Å )of phosphorus from a doped oxide containing 0.5 at.% phosphorus into steam oxide after heating for 30 min at 1000°C.

ISSN:0021-8979    

DOI:10.1063/1.1662969

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Recently published measurements of the gain in continuous‐wave CO2waveguide lasers have indicated that the small‐signal gain decreases exponentially with pressure in the range beyond about 70 Torr. In the present paper, the observed dependence of the gain on pressure has been incorporated into the general theory of homogeneously broadened gas lasers to form a phenomenological model of the waveguide laser. The model is then used to generate a series of curves intended to aid in the selection of gas mixture, operating pressure, discharge length, and mirror reflectivities when tunability is the primary design goal. The operating parameters are chosen on the basis of the desired laser characteristics (bandwidth and output power) and a small number of molecular parameters. Although the discussion emphasizes CO2waveguide systems, the design curves are applicable to all homogeneously broadened gas lasers. It is found that, although there exists a critical pressure beyond which the laser should not be operated for reasons of efficiency, the tunability can be increased indefinitely by incorporating a longer discharge and an appropriate tunable internal etalon.

ISSN:0021-8979    

DOI:10.1063/1.1662970

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Mechanisms for the nucleation of oxidation‐induced stacking faults in silicon have been examined. Fault nucleation is found to occur at sites of mechanical damage and at impurity inhomogeneities in the silicon. In either case, nucleation occurs by the coalescence of excess interstitials into Frank loops surrounded by dislocations of the type (a/3)(111). Nucleation in damage‐free crystals occurs along a banded or striated distribution. This is identical to the distribution of shallow noncrystallographic etch pits in the unoxidized wafer which have been linked to vacancy‐oxygen complexes. The common distribution pattern indicates that the impurity inhomogeneities are nucleation sites for fault formation. Models for the nucleation phenomenon are proposed based upon local excess oxygen diffusion into regions of excess vacancy concentration in the crystals.

ISSN:0021-8979    

DOI:10.1063/1.1662971

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The electrical characteristics of boron‐diffusedP+Ndiodes containing electrically active stacking faults (EASF) are investigated. The method combines an analysis of theI‐Vcharacteristics of the diodes with information derived from a scanning‐electron‐beam technique, the electron‐beam‐induced current (EBIC) mode. Stacking faults (SF) measuring 1–2 &mgr;m in length nucleate and develop in the near‐surface region of the silicon slice during the initial oxidation process. Subsequent to the boron diffusion, the SF are heavily decorated with impurity precipitates. Excess reverse currents are measured at room temperature over a broad range of voltage from the very‐low‐voltage region whereVR< kT/qto the high‐voltage preavalanche region whereVR≫kT/q. Two distinct regions are observed in theI‐Vcharacteristics of all diodes containing EASF's. These regions are separated by an effective threshold voltageVTHE, which is characteristic of the EASF's in the particular diode. For typical diodes with a junction depthXj=0.4 &mgr;m, experimentally determined values forVTHEare in the range 0.1–10.0 V. When the applied reverse voltageVR< VTHEthe diode exhibits the two regions characteristic of silicon diodes at room temperature; a low‐field Ohmic conductance region whenVR< k T/qand a space‐charge‐generation region whenVR> k T/q, which is similiar to a modified form of SNS theory. In this region, the excess generation currents are found to correlate with the threshold voltage of the EASF's. WhenVR> VTHEa voltage power‐law dependence is observed whereIR&agr;Vn, n≈4.75±0.25. This carrier‐generation effect results from the interaction between the strain field and/or the impurity atmosphere surrounding the EASF and the depletion field of theP Njunction. The composite defect introduces a local high‐density zone of g‐r centers which reduce the effective lifetime of minority charge carriers in the region of the SF. The localized g‐r zones are typically 20 &mgr;m2in cross‐sectional area with an effective lifetime of 4 – 400 ps. They are distributed nonuniformly, and are the direct source of excessIRcurrents measured at room temperature.

ISSN:0021-8979    

DOI:10.1063/1.1662972

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Although it is known that the small‐signal gain calculations are in agreement with experimental results of lowest threshold for the zero‐order mode in the thick‐cavityPpnNjunction laser, the theory for lasing mode stability under large‐signal conditions has not been previously investigated. In this paper, a study is given of the geometrical conditions under which the best dynamic stability is obtained for the lasing mode in a structure capable of supporting several modes. Solutions are obtained for the carrier and gain spatial profiles in the active region of an injection laser under large‐signal conditions by accounting for both spontaneous and stimulated recombination. The effect of stimulated emission in a lasing mode on the gain of a nonlasing mode is calculated. It is found that, for certain positions of thep‐njunction within the optical cavity, an increase in lasing power in the zero‐order mode suppresses the gain in higher‐order modes. The optimum geometry for dynamic stability of the lasing zero‐order mode is obtained when the gain region is two‐thirds of the waveguide thickness, consistent with the condition for lowest zero‐order mode threshold. In addition, the results also show that the quasi‐Fermi level in the gain region changes as a function of stimulated power in such a way as to keep its spatially ``averaged'' value nearly constant. However, the position of the quasi‐Fermi level at thep‐ninterface increases with increased optical power, thereby leading to a finite and positive junction differential resistance. Finally, for a double‐heterostructure (DH) laser the calculated internal conversion efficiency, which is the ability of the stimulated field to extract power from the junction, is shown to decrease significantly when the thickness of the active region exceeds a carrier diffusion length.

ISSN:0021-8979    

DOI:10.1063/1.1662973

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Granular metal‐semiconductor barriers were investigated onn‐type Si, GaAs, and CdSe single crystals. The barriers were formed by cosputtering metals, Au or Ni, and insulators, SiO2or Al2O3, onto the semiconductor surface. By varying the relative volume fraction of the insulator over the range 0–90%, the structure of the granular metal changed from that of a continuous metal to that of isolated small([inverted lazy s]20  Å )metallic particles embedded in the insulator. Even with as little as 10% by volume of the metal, the granular metal contacts were found to behave as metal‐semiconductor Schottky barriers. In the composition range 60–90% insulator in the granular metal, the barrier heights were independent of composition and their values were 0.57, 0.58, and 0.65 eV on Si, GaAs, and CdSe, respectively. In the case of Si and GaAs, the barriers are significantly lower than those observed for the pure metals; in the case of CdSe no such difference is found.

ISSN:0021-8979    

DOI:10.1063/1.1662974

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The absorption coefficients for InxGa1−xAs epitaxialn‐ andp‐type films have been determined for the composition range 0 <x< 0.25. The optical absorption coefficient is a parameter in the operation of negative electron affinity (NEA) photoemissive devices, and the experimentally determined absorption coefficient will be useful in the interpretation of NEA photoemissive device characteristics. In general, the optical absorption properties ofn‐ andp‐type InxGa1−xAs alloys vary smoothly with increasing indium content. The effect of lattice parameter mismatch between the InxGa1−xAs epitaxial film and GaAs or InxGa1−xP substrates on the optical absorption properties is shown to be negligible. Doping with zinc acceptor impurities([inverted lazy s]1019 cm−3)does, however, apparently change slightly the characteristics of the InxGa1−xAs absorption curves, particularly at low In compositions. Two nondestructive methods of determining the acceptor density of zinc‐doped GaAs epitaxial layers have been compared. The plasma minimum method is useful for acceptor concentrations above about 5 × 1018cm−3, while the free‐carrier absorption method gives quantitative values in the 1017–1019‐cm−3range.

ISSN:0021-8979    

DOI:10.1063/1.1662976

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Many physical occurrences are characterized by extremely low spectral variations, the measurement and estimation of which has been invariably difficult. An estimate of the density of the power spectrum of very‐low‐frequency semiconductor 1/fnoise is experimentally obtained from 10−6.3to 1.0 cps with a greater accuracy than that achieved in previous similar attempts; it is concluded that the spectrum is 1/f&agr;with &agr; approximately 1.3 over most of the frequency range, but appearing to have a value of about 1.0 in the lowest decade. A peculiar form of stationarity seems to distinguish 1/fnoise from other noise in semiconductors. Ten independent noise sources were time multiplexed and their spectral estimates were subsequently averaged. If the sources have similar spectra, this reduces the necessary data‐taking time by a factor of 10 for a given accuracy. An estimator is derived for optimal spectral estimation based on a number of statistically independent noise sources. Other related topics considered are nonequidistant sampling, and a plausible mathematical model of such flicker noise. Finally, the variance of the spectral estimate obtained through the Blackman/Tukey algorithm is analyzed in great detail; the variance is shown to diverge for &agr;≥1.0 in an assumed power spectrum ofk/|f|&agr;, unless the assumed spectrum is ``truncated''.

ISSN:0021-8979    

DOI:10.1063/1.1662977

出版商:AIP    

年代:1974

数据来源: AIP