摘要:

Results concerning the generation of recombination centers induced by rapid thermal annealing and by the combination of this heat pulse with an internal gettering process are reported. The influence of both the duration and the ambient of the rapid thermal annealing is studied by measurements of the minority‐carrier diffusion length. This work shows that (i) a short heat pulse at high temperature is sufficient to induce a strong degradation of this diffusion length. The activation of the pre‐existing impurities and a modification of the intrinsic defect population during the annealing may occur, (ii) the rapid thermal annealing has still an influence on the generation of recombination centers after thermal treatments at high temperature and for long durations. Indeed, this memory effect is observed even after the internal process, as observed in a previous work for the oxygen precipitation. However, we conclude that the recombination centers generated cannot be totally correlated with the oxygen precipitation. Introducing hydrogen during the RTA shows that the nature of defects responsible for the modification of the minority carrier diffusion length and oxygen precipitation must be different. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361142

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A thermodynamic model including four irreversibilities is used to investigate the optimal performance of a solar‐driven thermoelectric generator. The efficiency of the system is derived and taken as an objective function for optimization. Some important curves, such as the efficiency of the system versus the operating temperature of the solar collector, the reduced current, and the load resistance, are obtained. These curves can reveal the performance characteristics of solar‐driven thermoelectric generators. The maximum efficiency of the system and the corresponding reduced current are derived for some special cases. The optimal matching of load resistance which is one of the key problems in the optimal design of solar‐driven thermoelectric generators is discussed. New bounds of the key performance parameters, such as the efficiency, power output, and load resistance, are determined. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361143

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

By combining a low temperature (600 °C) chemical vapor deposition process for homoepitaxial diamond and conventional ion implantation, we have made and lifted off a synthetic diamond single crystal plate. Before growth, a type Ia C(100) crystal was exposed to a self implant of 190 keV energy and dose of 1×1016cm−2. Homoepitaxial diamond growth conditions were used that are based on water‐alcohol source chemistries. To achieve layer separation (‘‘lift‐off’’), samples were annealed to a temperature sufficient to graphitize the buried implant‐damaged region. Contactless electrochemical etching was found to remove the graphite, and a transparent synthetic (100) single crystal diamond plate of 17.5 &mgr;m thickness was lifted off. This free‐standing diamond single crystal plate was characterized and found to be comparable to homoepitaxial films grown on unimplanted single crystal diamond. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361144

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The multiphoton ionization of a low‐pressure (3×10−5Torr) fill of trimethylamine using an electron‐beam pumped KrF laser has been studied. A microwave resonator probe was used to measure the resultant free‐electron density. The scaling of electron density with the square of the incident laser intensity was verified in the low flux limit. The electron production decreased significantly from theI2scaling at laser fluxes exceeding 4 MW/cm2. These results are consistent with a simple two‐photon model describing the interaction in the low flux limit and a saturation of the electron production in the high‐flux limit. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361145

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Magneto‐oscillations due to a minority carrier two‐dimensional electron gas (2DEG) in the base of a bipolar quantum well resonant tunneling transistor at liquid helium temperatures are reported, we believe, for the first time. These are attributed to a high‐density 2DEG formed in the 20 nm undoped setback layer between the base and emitter. The 2DEG density has a nonmonotonic dependence on the emitter/base junction bias, increasing to a maximum at flatband conditions, then decreasing at higher bias. Associated lateral electron diffusion dominates recombination such that the current gain can increase 1000 times in a 6 T magnetic field. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361146

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present predictive and accurate modeling of base and collector currents in poly‐Si emitter bipolar transistors Ref. . Using a standard 0.8 &mgr;m bipolar complementary metal–oxide–semiconductor technology process flow Ref. , numerous experiments are performed. The base and emitter doping profiles are varied intentionally over a wide range in a controlled manner, so as to extract a self‐consistent set of apparent band‐gap narrowing, minority‐carrier mobility, intrinsic concentration parameter, and Auger recombination rate that is valid for simultaneously modeling bipolar transistor base and collector currents. The standard nature of the fabrication process technology chosen for this study allows the results to be more generally applicable. The doping concentrations for physical device simulations are taken directly from secondary‐ion‐mass spectrometry measurements. These profiles are then verified using spreading resistance measurements and capacitance–voltage measurements. It is shown that the measured base and collector currents for all experiments at room temperature can be fit simultaneously using Klaasen’s unified apparent band‐gap narrowing and mobility model Ref. . The emitter poly‐Si/epi‐Si interface (surface) hole recombination velocity is derived as a function of the emitter implant dose (arsenic concentration in the emitter) consistent with the model mentioned above. Sensitivity of the simulation results to model parameters is shown. It is further shown that the emitter implant dose can be used as a bipolar transistor optimization parameter. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361147

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Light‐emitting diodes made with poly(2‐methoxy‐5(2′‐ethyl)hexoxy‐phenylenevinylene) (MEH‐ PPV) using indium‐tin‐oxide (ITO) as anode and Ca as cathode have been examined as they age during operation in a dry inert atmosphere. Two primary modes of degradation are identified. First, oxidation of the polymer leads to the formation of aromatic aldehyde, i.e., carbonyl which quenches the fluorescence. The concomitant chain scission results in reduced carrier mobility. ITO is identified as a likely source of oxygen. The second process involves the formation of localized electrical shorts which do not necessarily cause immediate complete failure because they can be isolated by self‐induced melting of the surrounding cathode metal. We have not identified the origin of the shorts, but once they are initiated, thermal runaway appears to accelerate their development. The ultimate failure of many MEH‐PPV devices occurs when the regions of damaged cathode start to coalesce. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361096

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present a theory of tunable infrared response in field‐effect transistors. The linear &agr;(&ohgr;) and second‐order &bgr;(&ohgr;) polarizability are calculated numerically as functions of frequency of an applied electric field. Transitions between electron subbands in the inversion layer cause resonances in the frequency response, which are tunable with a gate voltage. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361101

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present results from numerical simulations of AlGaN/InGaN double‐heterostructure light‐emitting diodes. A highly convergent, fast, and memory efficient algorithm necessary for wide band‐gap device simulation was developed and is described here. Charge carrier tunneling currents and a band to impurity recombination mechanism are included. The results compare favorably to experimental results. The results demonstrate that the saturation of power at high currents, the high rate of increase in currents at high voltages, and the reduced broadening of the optical emission spectrum at high biases, with only band‐to‐acceptor recombination occurring in the active region, are due to carriers leaving the active region by thermionic emission rather than recombining. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361148

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The flux method of McKelvey, Longini, and Brody [Phys. Rev.123, 51 (1961)] is used to analyze current blocking in double‐heterostructure bipolar transistors with composite collectors (CC). The effects of electron accumulation in the spacer layer are included; these are shown to impose an intrinsic limit on the simplest CC design. The analysis is extended to include compositional or band‐gap grading, which can substantially reduce the current blocking at high currents, though it has less effect at lower currents. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361107

出版商:AIP    

年代:1996

数据来源: AIP