摘要:

A finite charging energy,e2/2C’, is required in order to place a single electron onto a small isolated electrode lying between two tunnel junctions and having a total capacitanceC’to its external environment. Under suitable conditions, this elemental charging energy can effectively block all tunnel events near zero bias voltage in series arrays of ultrasmall junctions, an effect that has come to be known as the ‘‘Coulomb blockade.’’ This article outlines a new approach to the design of digital logic circuits utilizing the Coulomb blockade in capacitively biased double‐junction series arrays. A simple ‘‘on’’/‘‘off ’’ switch is described and complementary versions of this switch are then employed to design individual logic gates in precise correspondence with standard complementary metal–oxide semiconductor architecture. A planar nanofabrication technique is also described that may eventually allow the integration of Coulomb blockade logic onto conventional semiconductor chips, thereby realizing hybrid integrated circuits having device densities and operating speeds far in excess of present technology.  

ISSN:0021-8979    

DOI:10.1063/1.352206

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new GaAs switching device with a triple‐well superlattice emitter structure, prepared by molecular beam epitaxy, has been fabricated and demonstrated. An S‐ and N‐shaped negative‐differential‐resistance (NDR) phenomenon, attributed primarily to the avalanche multiplications process and resonant‐tunneling effect, were observed simultaneously when a proper collector‐emitter voltage (VCE) was applied. The operation temperature is known from the experimental results to play an important role on the influence of the NDR behaviors. A transistor action with a common‐emitter current gain of over 36 was also achieved at 300 K when a control current was employed to the base electrode. This device exhibited a significantly regenerative switching phenomenon both at room temperature and low temperature if a −VCEvoltage was used. The proposed structure consequently has good potential for switching and quantum functional device applications.

ISSN:0021-8979    

DOI:10.1063/1.352207

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

S‐type switching characteristics have been observed at room temperature in AlAs/GaAs multiquantum well diodes at low forward bias. The multiquantum well structure consisted of a set of 10 periods of undoped 50‐nm AlAs barriers with 50‐nmn+(1×1018/cm3) GaAs quantum wells inserted between ap+‐GaAs anode andn+‐GaAs cathode. A threshold voltage for switching from the low to high conductance state of 2.2 V was measured and a minimum holding voltage in the high conductance state of 0.9 V was observed. Switching to the high conductance state occurs due to impact ionization of electrons out of the heavily dopedn+wells forming positive space charge which enhances the cathode field and thereby electron injection giving rise to a positive feedback mechanism.  

ISSN:0021-8979    

DOI:10.1063/1.352208

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The split cavity oscillator (SCO) is a resonant cavity device which can be used to modulate the current of a relativistic electron beam. The modulated electron beam can be used to produce high‐power microwaves. The SCO consists of a cylindrical cavity resonator which has been divided (split) into two identical regions (cavities) by a thin conducting foil (or screen) whose radius is less than the inner radius of the cylinder. The resulting gap between the foil perimeter and inner cylinder wall forms an annular slot which couples the cavities electromagnetically. The SCO supports standard transverse magnetic (TM) modes, in addition to split cavity TM modes. The latter will interact unstably with an electron beam, thereby producing a high degree of current modulation in a short distance. For the purpose of characterizing split cavity TM modes, and developing a design tool for SCOs, a cold dispersion relation (no electron beam) is derived by solving Maxwell’s equations for the fields in an equivalent periodic structure. The dispersion relation and field solutions are employed to numerically calculate eigenfrequencies and eigenfunctions for the SCO. The latter are used to develop predictive formula for the SCO oscillation frequency, and to gain some understanding of the interaction that takes place when an electron beam is present.

ISSN:0021-8979    

DOI:10.1063/1.352209

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We present a detailed and thorough study of a wide variety of quantum well infrared photodetectors (QWIPs), which were chosen to have large differences in their optical and transport properties. Bothn‐ andp‐doped QWIPs, as well as intersubband transitions based on photoexcitation frombound‐to‐bound,bound‐to‐quasicontinuum, andbound‐to‐continuumquantum well states were investigated. The measurements and theoretical analysis included optical absorption, responsivity, dark current, current noise, optical gain, hot carrier mean free path, net quantum efficiency, quantum well escape probability, quantum well escape time, as well as detectivity. These results allow a better understanding of the optical and transport physics and thus a better optimization of the QWIP performance.

ISSN:0021-8979    

DOI:10.1063/1.352210

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The stability of an amorphous GexSi1−xO2in contact with an epitaxial (100)GexSi1−xlayer obtained by partially oxidizing an epitaxial GexSi1−xlayer on a (100)Si substrate in a wet ambient at 700 °C is investigated forx=0.28 and 0.36 upon annealing in vacuum at 900 °C for 3 h, aging in air at room temperature for 5 months, and immersion in water. After annealing at 900 °C, the oxide remains amorphous and the amount of GeO2in the oxide stays constant, but some small crystalline precipitates with a lattice constant similar to that of the underlying GeSi layer emerge in the oxide very near the interface for bothx. Similar precipitates are also observed after aging for bothx. The appearance of these precipitates can be explained by the thermodynamic instability of GexSi1−xO2in contact with GexSi1−x. In water at RT, 90% of GeO2in the oxide is dissolved forx=0.36, while the oxide remains conserved forx=0.28.

ISSN:0021-8979    

DOI:10.1063/1.352211

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report the fabrication of high quality Ga0.8In0.2As/GaAs/Ga0.51In0.49P multiple quantum well laser emitting at 0.98 &mgr;m grown by low pressure metalorganic chemical vapor deposition. Continuous wave operation with output power of 500 mW per facet was achieved at room temperature for a broad area laser with 130 &mgr;m width and 300 &mgr;m cavity length. This is an unusually high value of output power for this wavelength laser in this material system. The differential quantum efficiency exceeded 75% with excellent homogeneity and uniformity. The characteristic temperature,T0was in the range of 120–130 K.

ISSN:0021-8979    

DOI:10.1063/1.352212

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We report on the identification of the CuGaacceptor level as a recombination center in GaAs. Using time‐resolved photoluminescence (PL) we have studied the recombination of excess charge carriers in metalorganic vapor‐phase epitaxy GaAs/AlGaAs double heterostructures. The recombination in one particular set of samples was clearly nonradiative and the trap level derived from our measurements coincides with that of CuGaas seen in the PL spectra. The temperature dependence of the capture coefficients is consistent with a multiphonon process and allows for the determination of the coupling strength for electron and hole capture.

ISSN:0021-8979    

DOI:10.1063/1.352184

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

X‐ray reflectometry and double‐crystal diffraction have been applied to the characterization of molecular beam epitaxy‐grown Si/Si1−xGexsuperlattices. It is shown, using specific examples, how reflectometry can help to solve difficulties encountered in double‐crystal diffractometry analysis of nonideal superlattices that contain thickness fluctuations or in which partial strain relaxation has occurred.

ISSN:0021-8979    

DOI:10.1063/1.352185

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

The characteristics of geometric dimensions, such as the modulation lengthL, the central guide widthW, and the gapGbetween the central guide and antiguide regions for the performance of the guide/antiguide intensity modulator have been examined. Both theoretical predictions and experimental measurements are reported here.  

ISSN:0021-8979    

DOI:10.1063/1.352186

出版商:AIP    

年代:1992

数据来源: AIP