摘要:

The dependence of electron diffusion length on the excitation and impurity compensation in thepregion of a GaAs junction laser has been calculated from the band theory of impure semiconductors. Using a screened potential for each impurity atom, the average room‐temperature diffusion length in a typical diffused diode is found to be 1.4 &mgr; at low injection limit. The diffusion length increases with increase in excitation because of the enhancement in carrier screening and carrier diffusion energy. This effect can be used to explain the much lower threshold current in an AlxGa1−xAs&sngbnd;GaAs heterostructure laser and an abnormally high threshold current in a shallow diffused homostructure laser. Furthermore, the electron diffusion length is found to be larger for the region near the junction due to longer electron lifetime in this region. This also explains the observation that in a normal diffused junction laser, the active region occurs somewhere in thepregion but not right next to the space‐charge region.

ISSN:0021-8979    

DOI:10.1063/1.1660092

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Potential measurements as a function of time and space show in detail the passage of an injected electron‐hole plasma front, and the eventual establishment of a nonequilibrium steady state in a long bar ofp‐type InSb at 77°K. The front is preceded by a depletion layer which vanishes as plasma reaches the anode. Thereafter the current, with the voltage held constant, grows exponentially until just before the steady‐state plasma density is reached. These results are compared with a theory by Dean and by Ancker‐Johnson, Robbins, and Chang describing plasma injection into a semiconductor with deep traps. The measured front arrival time as a function of constant applied voltage agrees satisfactorily with Dean's prediction. Four observations are at variance with his theory: the time constants of the exponential current growth are density‐dependent instead of being independent as predicted; the current at the front arrival is not a function of voltage as his theory states; the electric field behind the front is not proportional to the square root of distance; and the steady‐state injected current has a higher power dependence on voltage than the predicted square‐law dependence. The extended analysis accounts for all the observed growth time behavior, namely a growth time which is independent of steady‐state density at high and low densities, and which increases with density in the intermediate range. Also, a new theory of the steady‐state conduction characteristic, based on the density‐dependent plasma lifetime, reproduces quite well the measured conduction characteristics,I∝Vnwith 2<n<8, until the interference of pinching, which causes a sub‐Ohmic conduction. In the nonequilibrium steady state the plasma density has a uniform spatial distribution within a factor of two over the central 80% of the sample length. The steady‐state density decreases monotonically from cathode to anode, or alternatively, a U‐shaped distribution is observed with high plasma densities occurring also at the anode, a characteristic which is attributed to copious hole injection. All the observed dynamic and steady‐state properties of double injection intop‐InSb are in good agreement with theory except for the constancy of the current magnitude at the front arrival and the form of the dependence of electric field on distance.

ISSN:0021-8979    

DOI:10.1063/1.1660093

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

This paper introduces an impulse technique, utilizing either electrical or optical excitation, capable of giving new information concerning the properties of luminescent systems. An analysis is included for both types of excitation and experimental results utilizing electrical excitation are reported. In particular it is shown that minority carrier lifetime in the active electroluminescent region can be evaluated directly. The technique is applied to red emitting GaP (Zn&sngbnd;O) electroluminescent diodes excited with short, <2 nsec, current pulses. The resulting time‐dependent luminescent response is then interpreted using a phenomenological model previously evolved. This model assumes that bound exciton radiation dominates the luminescent process at room temperature, where the experiments were carried out. Utilization of this theory allows the extraction of several of the important parameters of the radiative and nonradiative recombination processes. Minority carrier lifetimes between 3 to 10 nsec have been deduced for particular diodes, in good agreement with values previously reported. In addition, the experimental results can be interpreted as placing an upper bound on the hole equilibration time which is sufficiently small that it permits a significant simplification of the recombination kinetics in GaP.

ISSN:0021-8979    

DOI:10.1063/1.1660094

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Transferred‐electron bulk‐negative‐differential‐conductivity devices with nonuniform geometry, field, and doping distributions are analyzed. Numerical solutions of the conduction equations was possible due to the novel scheme introduced to account for the area variation in the direction transverse to the electron flow. The simulation results show that the space‐charge travel can be controlled with the applied bias voltage for concentric and some other nonuniform geometries. This results in the possibility of tuning the frequency over two octaves. The nature of the frequency control characteristic is shown to be dependent on the device geometry. Dipole space‐charge nucleates due to nonuniform geometry without any necessity of initialization or doping fluctuations. Multiple space‐charge formation is observed to occur in an oscillation cycle as a result of sequential decay processes. Space‐charge modes in nonuniform geometries display polarity dependence. Divergent and convergent geometries are shown to favor dipole and accumulation‐type space charges, respectively. Analysis of devices with doping gradients demonstrate the equivalence of these gradients to the geometry nonuniformities. The analytical solutions of the conduction equations indicate the simple dependence of the space‐charge behavior on the geometry. The space‐charge nucleation, growth, propagation, and decay are related to the time variation of the cathode field and the domain voltage.

ISSN:0021-8979    

DOI:10.1063/1.1660095

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A tuning‐initiated failure has been observed in silicon avalanche diode oscillators operated in the Trapatt mode. The precise nature of the failure mechanism remains to be established but several possibilities, based on experimental evidence, are discussed. The circuit‐tuning conditions necessary to initiate the failure (burnout) and the physical state of the diode after the failure are described. A gold whisker, which shorts the junction, is found extending from the mounting stud contact. Preliminary evidence indicates that the shape of the junction region, as controlled by the etching process, can be tailored to inhibit such diode failure.

ISSN:0021-8979    

DOI:10.1063/1.1660096

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The temperature dependence of the Hall coefficient and resistivity is presented on samples which show an anomalous behavior and the effects of various surface treatments on the electrical properties is examined. The anomalous effects have been eliminated in a few cases by proper heat treatments yielding normalp‐type Hall coefficients down to 4.2°K. Field effect measurements confirm that these effects are due to ann‐type inversion layer on the surface ofp‐type Hg0.8Cd0.2Te. Surface carrier concentration in this inversion layer ranges from 1×1012/cm2to 5×1012/cm2and mobility in this layer was found to be in the 103cm2/V·sec range.

ISSN:0021-8979    

DOI:10.1063/1.1660097

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The current waveforms obtained by exploding various sizes of copper wires by the discharge of a large condenser bank revealed that the (V, l) plane (V=initial voltage,l= length of the wire) can be divided into various zones with each zone characterising a particular type of explosion. In particular the current pause was observed only in one zone. Below a certain initial voltage no pause in the current could be induced. The restrike length of enamel insulated wires was found to be considerably more and the pause duration considerably less than for bare wires. In this case thermally emitted electrons trapped in the insulation are considered responsible for a reduction in the pause duration and an increase in the restrike length. The increased restrike current for enamel insulated wires vis a vis bare wires may be due to the arc shunting as suggested by the current wave forms obtained from exploding coils. The energy absorbed by an exploding coil depends upon its pitch.

ISSN:0021-8979    

DOI:10.1063/1.1660098

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A series of 0.2‐ to 3‐gm HNS charges were detonated in vacuums of 10−3to 10−5Torr. The resultant freely expanding, detonation product, gas blast achieves terminal velocities of 8 to 12 km/sec within 3 to 5 &mgr;sec after the detonation wave arrives at the free surface. Measured pressure profiles display rise times to maximum stagnation (``reflected shock'') pressure varying from ∼30 &mgr;sec, 20‐cm away from a 2.6‐gm charge, to ∼185 &mgr;sec, 127‐cm away from 0.2‐gm charge at 10−5Torr. Rise times were generally shorter at 10−3and 10−4Torr; the 10−5Torr values agree with numerical calculations. Using cube root scaling of charge mass, the observed peak reflected pressure as a function of range may be represented byp=6.5×105 (bar) r′−3.5,wherer′the ratio of the range to the equivalent charge radius.

ISSN:0021-8979    

DOI:10.1063/1.1660099

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Using a set of commercially prepared sodium ferrocyanide absorbers enriched to 91.2% Fe57the Lamb‐Mo¨ssbauer factor was measured to be 0.28±0.03. The thickness of Fe57for these absorbers was measured using x‐ray absorption techniques and was found to be considerably smaller than that advertised by the manufacturer even after correcting for the size of the ferrocyanide particles in the absorbers.

ISSN:0021-8979    

DOI:10.1063/1.1660100

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Ge films were made at 5×10−6Torr by an oblique deposition. Resistivity and its change due to oxygen exposure were measured for different deposition angles. Resistivity anisotropy and its change caused by oxygen exposure were also measured. They increased with the deposition angle. The mass of the film was measured by a microbalance and its density was calculated. The density of the film was less than that of bulk and became smaller with an increase of the deposition angle. These phenomena are explained by the self‐shadowing effect.

ISSN:0021-8979    

DOI:10.1063/1.1660101

出版商:AIP    

年代:1971

数据来源: AIP