摘要:

The dc characteristics of modulation‐doped AlxGa1−xAs/GaAs field‐effect transistors have been studied experimentally and theoretically to determine the effect of the thickness of the undoped AlxGa1−xAs spacer layer commonly left at the heterointerface. Increasing the thickness of the spacer layer decreases charge transfer and increases mobility. Current transport in short channel transistors, however, is limited by the electron saturation velocity which is independent of the spacer thickness. Due to increased charge transfer, decreasing the spacer thickness from 100 to 20 A˚ doubled the maximum saturation current and transconductance. This should allow faster switching speeds to be obtained. A maximum current of 24 mA was obtained for a gate width of 145 &mgr;m with a 40‐A˚ spacer and a transconductance of 250–275 mS/mm was obtained for a device with a 20‐A˚ spacer. Theoretical results indicate that intrinsic transconductances greater than 900 mS/mm are possible. Preliminary small‐signal rf measurements indicate a maximum available gain of about 9 dB at 8 GHz.

ISSN:0003-6951    

DOI:10.1063/1.93908

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Schottky barrier heights for aluminum‐(100) GaAs diodes with and without an interfacial native oxide layer have been evaluated using Norde’s method of current‐voltage analysis. Barrier heights determined by Norde’s method on sputter‐annealed, oxide‐free substrates are systematically lower (0.53–0.59 eV) than values determined by photoresponse measurements (0.78±0.03 eV). Anomalous structure in the form of a second minimum was observed in the Norde plots for unsputtered substrates on which a thin native oxide was present. The barrier heights obtained from the second minimum observed at high forward bias (∼0.75 V) were 0.90–0.95 eV, whereas photoresponse measurements indicated barriers of 1.00±0.01 eV.

ISSN:0003-6951    

DOI:10.1063/1.93909

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Antenna‐coupled point contactn‐Ge/tungsten Schottky diodes have been used to detect CO2laser radiation, and a very clear antenna pattern is obtained for an electric field polarized in the plane of incidence. The polarity of the detected voltage of the diode at low frequency and CO2laser frequency regions indicates that the nonlinearI‐Vcharacteristic of the diode at low frequency persists up to the CO2laser frequency.

ISSN:0003-6951    

DOI:10.1063/1.93910

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The effect of orientation on self‐aligned source/drain planar GaAs Schottky barrier field‐effect transistors (FET’s) has been investigated. The dependence of the threshold voltage of FET’s on gate length was measured for FET’s oriented in two perpendicular [110] directions. Both stress‐enhanced lateral spread of implanted ions and lateral diffusion at the gate material/GaAs interface are proposed as possible mechanism to account for the orientation effect. The experiments indicate that the preferred direction for the self‐aligned FET fabrication on a (100) substrate is [011¯].

ISSN:0003-6951    

DOI:10.1063/1.93911

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A low‐temperature (30–250 °C) technique for depositing thin films of stoichiometric, amorphous dielectric layers with a sharp interface between the film and the substrate is proposed and demonstrated. The technique uses a combination of atomic or molecular beams of which at least one of the sources is generated by a plasma. As examples, SiO2and Al2O3films have been deposited on Si, GaAs, InP, InGaAs substrates. It is shown that the interface between the dielectric and the semiconductor is extremely sharp and that no native growth of oxides occurred on the semiconductor surface during film deposition. The physical properties of the deposited SiO2are nearly identical to those of thermal oxides grown on Si. Preliminary electrical properties show that the films have a breakdown field strength of about 5×106V/cm, and the 1‐MHzC‐Vcurves shown hystereses of 50 mV with a sweep rate of 100 mV/s. The fixed charge density is about 3.5×1011cm−2.

ISSN:0003-6951    

DOI:10.1063/1.93912

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

By using infrared absorption, photoluminescence, and Hall measurements we have observed an additional level associated with a residual acceptor in liquid encapsulated Czochralski GaAs. These results indicate that the defect is a double acceptor with levels 78 and 200 meV above the valence band.

ISSN:0003-6951    

DOI:10.1063/1.93913

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Electroluminescence excited by infrared radiation has been observed in GaP light‐emitting diodes (LED’s) at low temperatures providing a new efficient method to convert infrared radiation within a broad spectral range into visible light. Using 10.6‐&mgr;m radiation of a CO2laser an up‐conversion quantum efficiency of 3.4×10−6was found. If a low dark current photomultiplier is employed to detect the LED emission the dominant noise source is due to conversion of thermal background radiation yielding a noise equivalent power of NEP=1.6×10−9W/Hz1/2.

ISSN:0003-6951    

DOI:10.1063/1.93914

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The origin of the difference in the open circuit voltageVocbetween ap‐i‐nandn‐i‐ptype hydrogenated amorphous silicon solar cells is discussed theoretically, considering the interaction of photogenerated free electrons and holes, i.e., the effect of a self‐field. It has been clarified that the self‐field aids the carrier collection in ann‐i‐pcell whereas it impedes the carrier collection in ap‐i‐ncell. This difference in the effect of the self‐field on the photovoltaic process causes the difference inVocbetween these two type cells.

ISSN:0003-6951    

DOI:10.1063/1.93915

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Nanosecond resolution time‐resolved x‐ray diffraction measurements have been used to study the temperature and temperature gradients in ⟨100⟩ and ⟨111⟩ oriented silicon crsytals during pulsed laser annealing. Thermal strain analysis of time‐resolved extended Bragg scattering has shown the lattice temperature to reach the melting point during 15‐ns, 1.5‐J/cm2ruby laser pulses and to remain at the melting point during the high reflectivity phase (HRP). The temperature gradients at the liquid‐solid interface were found to be in the range of ∼107K/cm during the HRP.

ISSN:0003-6951    

DOI:10.1063/1.93880

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An experimental technique has been developed to study the electrical properties of semiconductor grain boundaries (GB’s) by a focused laser beam. The laser beam is trained on a GB while the photoconductivity of the sample is measured. This technique allows us to examine a localized region of an individual GB in semiconductors with multiple grains. The measurement of the steady state and transient signals as a function of temperature determines the grain boundary barrier height, trap energy, and capture cross section.

ISSN:0003-6951    

DOI:10.1063/1.93881

出版商:AIP    

年代:1983

数据来源: AIP