摘要:

The electron capture time in single quantum wells is calculated by considering capture and escape as scattering events in Monte Carlo simulation. The calculation is performed for an AlGaAs/GaAs quantum well as a function of the well width at 300 K. The overall capture time of carriers is found to be controlled by the transition from the free state to the uppermost confined levels. Subsequent interband transitions cause rapid decay into lower levels. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364425

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A model is presented for the performance of quantum well infrared photodetectors (QWIPs) utilizing intersubband electron transitions and tunneling injection electrons. The dark current and the responsivity are derived as functions of the QWIP parameters, including the number of the QWs, in an analytical form. Nonlinear effects in the QWIP operation at high infrared power are considered and the threshold value of power density is estimated. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364426

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this article, we report on the characterization of a photovoltaic detector based on ann-type GaN Schottky barrier. We first present the photovoltaic responsivity above the gap. Its spectrum is explained by the combined effects of absorption and diffusion. The hole diffusion length is estimated to be in the 0.1 &mgr;m range with a numerical model. The photoresponse below the gap is also investigated and it is shown that the current generated by the internal photoemission is the major contribution to the photocurrent at reverse biases at 80 K. At room temperature, an additional component to the photocurrent is clearly demonstrated and identified. This extra current stems from the existence of traps. Several spectroscopy techniques are used to characterize those traps. The supplementary current emitted from the traps in the depletion region accounts for the spectral and the temporal behavior of the Schottky photodetector at room temperature. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364427

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Local doping with focused laser beam writing was used to fabricate lateralnpn- andpnp-structures on modulation-doped Si/SiGe heterostructures. The electrical and optical properties of the achieved lateral potential modulation were analyzed for local B-doping onn-type Si/SiGe and P- and Sb-doping onp-type SiGe/Si. Focused laser beam written doped lines show a strongly nonohmicIVcharacteristic indicating the formation of a local insulating barrier in the two-dimensional carrier system. Such lateral structures can be used as photosensitive devices with responsivities up to106 A/Wcombined with a spatial resolution on the &mgr;m scale. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364428

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The photoinduced transient current from an amorphous silicon thin-film transistor is computed and the mechanism described in terms of trap-state filling dynamics. The direction of the current flow and the location of the transient peak depends strongly on the distributions of donorlike and acceptorlike trap states in the neighborhood of the dark Fermi level. We show that the transient current can flow in the same direction as in the crystalline transistor, as well as in the opposite direction. There is also an interesting cross-over behavior in which the transient current flows out of the drain terminal as a pulse of positive charge, and then immediately reverses its direction. There is a broadening effect of the transient peak by a simultaneous switch on of the gate voltage. The transient peak typically occurs at10−4 sand an example is provided. The transient current can be greatly diminished by switching the gate voltage long before illumination, or by doping the channel either partially or completely. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364429

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the fabrication of polymer grid triodes (PGTs) usingC60as the semiconducting medium. The structure, a self-assembling porous conducting polyaniline network placed between two semiconducting layers ofC60,and sandwiched between two metal electrodes, demonstrates theI–Vcharacteristics of a three terminal device in which the current is controlled by the grid potential. As a result of the higher mobilities of the fullerenes compared to those of conjugated polymers, the fullerene devices offer some performance advantages; the operating voltages are less than 5 V with current densities exceeding1 mA/cm2.By fabricating devices with different grid densities, it is shown that the grid exhibits a strong influence on theI–Vcharacteristics for high grid densities, and a correspondingly low influence for low densities, in agreement with theory. TheI–Vcharacteristics of theC60PGTs are well described by an effective diode model, similar to that used for vacuum triodes. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364430

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

By application of a specially designed trigger electrode on which a laser beam is focused, it is possible to obtain a reliable method for initiation of high voltage vacuum discharges. The trigger electrode plasma generated by the laser beam has been studied with regard to its light emission. The result proved that the light intensity reaches its peak value about 200 ns after application of the laser trigger pulse. In addition, by using the triggering method presented, investigation of the high voltage vacuum discharge characteristics—current derivative(dI/dt),current, and x-ray output versus time—has been carried out. Recorded traces indicate pinching of the inter-electrode discharge channel but also x-ray emission during this event. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364431

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Thermal nitridation of thin amorphous Ti-silicide films is studied. The use of hydrazine gas enables the nitridation at 500 °C, well below the nucleation temperature of Ti silicide. Transmission electron microscopy reveals that these TiSiN fims have amorphous structures, which are shown to be stable up to 750 °C. X-ray photoelectron spectroscopy indicates the simultaneous formation of Ti–N and Si–N bonds. This is consistent with the Ti–Si–N ternary phase diagram. Further, the presence of this nitrided film between Al and Si retards the interfacial reaction up to an annealing temperature of 550 °C near the eutectic point (577 °C) of an Al–Si system. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364432

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The authors report on a systematic procedure for optimizing the second order susceptibility in semiconductor quantum wells (QWs) based on ternary alloys. The procedure relies on combining the supersymmetric and the coordinate transform methods. Optimized design ofAlxGa1−xAsbased QWs gives nonlinearity somewhat larger than is presently achieved in this system. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364433

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present experimental results from infrared photocurrent measurements at the Si/metal andSi/SiO2/metalinterface. We observe internal photoemission from the Si valence band into metal states or into empty interface states. For thep-Si/SiO2/metalinterface the photocurrent threshold occurs at a photon energy of 0.138 eV, indicating that the Fermi level is pinned close to the valence band. We argue that this is the case only for discrete locations of the interface and suggest that the pinning is caused by a defect-related acceptor level. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364434

出版商:AIP    

年代:1997

数据来源: AIP