摘要:

The minority carrier lifetime in a phosphorous‐diffused layer of a conventional N+/P silicon photocell has been investigated experimentally. The photovoltages have been measured as a function of photon flux density from low to medium illumination levels. From the quasi‐Fermi level analysis of Gray‐Kao‐Schroder, we have determined the carrier recombination lifetime as a function of the photogeneration rate ⟨G⟩ in the heavily‐doped N+layer. When the band gap narrowing effect is taken into consideration, the recombination processes can be described by (i) a ’’positive‐field controlled’’ Shockley‐Reed‐Hall recombination at low photo injection level, (ii) a ’’positive‐field influenced’’ Auger recombination at the medium injection level, and (iii) a ’’negative‐field controlled’’ Auger recombination at the high injection level. Under a very high photoexcitation condition, the magnitude of the saturated open circuit voltage of the cell is limited by the recombination lifetime at the surface contact region.

ISSN:0021-8979    

DOI:10.1063/1.329955

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Heating a Mg/Zn3P2Schottky solar cell in air results in the formation of ann/pjunction due to the diffusion of Mg in Zn3P2. The cells are fabricated on large grain polycrystalline Zn3P2wafers. The junction depth is determined from the change in the measured collection efficiency of the cell after heating and follows a (time)1/2dependence. The diffusion coefficient has been measured in the temperature range of 75–150 °C. The short‐circuit current and open‐circuit voltage of the homojunction qualitatively follow the theoretical predictions. A diffusion voltage of 1.2 V and a maximum open‐circuit voltage of 0.6 V have been achieved.

ISSN:0021-8979    

DOI:10.1063/1.329956

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Prior attempts at determination of the intrinsic density in GaAs are reviewed, and this quantity is then deduced anew from the temperature dependences of the intrinsic gap and of the valence and conduction band system statistical weights. The nonparabolicity of the lowest conduction band, and the effects of the next two conduction bands, are taken into account in deducingni(T) for the range 250–1500 K. That procedure gives a room‐temperature valueni(300) = 2.1×106cm−3, which can be compared with prior values from various experimental methods. The magnitude and temperature dependence ofniare then calculated by a different and entirely new method, which utilizes experimental data of the electron and hole emission and capture coefficients associated with Cr2+?Cr3+transitions of the substitutional CrGadeep‐level impurity in GaAs. Recent data of Martinetal. concerning these coefficients permits a deduction ofni(T) = 1.05 ×1016T3/2 exp(−0.802/kT) cm−3for 300<T<475 K, a range in whichniincreases from 2×106cm−3to 3×1011cm−3. Throughout that range, the procedure givesnilying within ±15% of that calculable ’’directly’’ from band gap and effective mass parameters.

ISSN:0021-8979    

DOI:10.1063/1.329958

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The Hall mobility and carrier concentration have been measured on low‐resistivity ZnSe epitaxial films in the temperature range of 77–300 K. Both undoped and indium doped materials were studied. Resistivities of the as‐grown films varied from 10−1to 105&OHgr; cm. Electron mobility was of the order of 10–200 cm2 V−1 s−1and was limited by ionized‐impurity scattering. Analysis of the temperature dependence of the carrier concentration and Hall mobility indicated that then‐type films were heavily compensated having acceptor concentrationsNA≳1018cm−3. It was found that the acceptor and donor concentrations were essentially independent of Zn/Se pressure ratio present during growth.

ISSN:0021-8979    

DOI:10.1063/1.329959

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The interface properties of the thermal nitride film‐InP system and its annealing were investigated. To obtain a uniform thermal nitride on a InP crystal, an improved thermal nitriding technique was developed by introducinginsituHCl vapor etching prior to the thermal nitriding. Two devices [MANS (metal‐alumina‐nitride‐semiconductor) diode and FET (field‐effect‐transistor)] containing a composite gate insulator of a thin nitride film (∼100 A˚) and CVD (chemical‐vapor‐deposition)‐Al2O3film (∼1000 A˚) were compared with conventional MAS devices in view of the surface state density (NSS) in the MANS interface at energies near the conduction band edge decreased from 1×1013to 1×1012/cm2eV after annealing at 550 °C. A considerable increase in the effective mobility of the MANS‐FET was also seen after annealing. However, further annealing at a temperature higher than 600 °C resulted in a gradual degradation in the interface quality. In contrast, only the MAS interface showed degradation. Discussions are given on the effects of annealing on interface properties of MANS and MAS devices, from the view point of surface passivation.

ISSN:0021-8979    

DOI:10.1063/1.329914

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The ⋅Si≡Si3defect revealed by electron spin resonance (ESR) at the Si/SiO2interface has been found to be very sensitive to ultraviolet (UV) radiation at 2537 A. With native oxides or very thin thermal oxides, UV bleached the signal, which then recovered slowly in room temperature air, or rapidly upon water immersion. Details of the bleaching suggest outer‐oxide surface trapping by adsorbed oxygen, rather than bulk oxide traps. In HF‐stripped silicon, an opposite uv effect was observed, i.e., an accelerated growth of ⋅Si≡Si3centers. The physico‐chemical responses of ⋅Si≡Si3reflected several stages in the development of nascent oxides on silicon wafers. The uv trapping phenomenon further offers a potential method for determination of the energy levels of the ⋅Si≡Si3defect, and thus for clarification of its role in interface trapping.

ISSN:0021-8979    

DOI:10.1063/1.329915

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A method is described for measuring the surface conductivity of insulating thin films. The conductivity is determined by observing the current transients while charging a capacitor whose dielectric is the insulating material and part of whose top electrode is the insulator surface. No elaborate sample preparation or experimental apparatus is required. Results are presented for oxide thermally grown on silicon, where sheet resistances between 1016and 1020&OHgr;/&laplac; were obtained for different values of relative humidity. The method can also be applied to a thin conducting layer on top of a thicker insulating film.

ISSN:0021-8979    

DOI:10.1063/1.329916

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

A new technique has been developed which directly measures carrier transport through the interfacial region at metal‐semiconductor (M‐S) contacts. The injection current is determined by measuring with fast time resolution the initial rate of decay of surface potential as charge at the surface is injected. Contact performance can be studiedinsituusing model M‐S systems constructed in ultrahigh vacuum, on single crystals cleaved in ultrahigh vacuum. The effect of foreign atoms adsorbed at the Al‐CdS interface is presented as an illustration of the technique. For the first time, injected dark currents through the clean interface are found which approximate trap‐free space‐charge‐limited values. Injection is continuously reduced by orders of magnitude as air exposure of the interface is increased during the formation of the M‐S contact. Steady‐state techniques are insensitive to this contact performance, due to bulk phenomena. The experimental design and performance of the time‐resolved charge injection technique are described in detail. Features of time resolution and initial‐field uniformity make this a particularly useful probe of complex M‐S interfaces.

ISSN:0021-8979    

DOI:10.1063/1.329917

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

The decrease of the work function of chromium and stainless steel due to hydrogenation has been observed. The consequences of hydrogenation of metals, which occurs when they are used as electrical contacts in solar cells made from hydrogenated amorphous silicon, are discussed.

ISSN:0021-8979    

DOI:10.1063/1.329918

出版商:AIP    

年代:1982

数据来源: AIP

摘要:

Thin‐oxide (40–50 A˚) metal oxide semiconductor (MOS) structures are shown to exhibit, prior to large levels of electron tunnel injection, the near‐ideal behavior predicted for a uniform trapezoidal barrier with thick‐oxide properties. The oscillatory field dependence due to electron‐wave interference at the Si/SiO2interface indicates an abrupt, one‐monolayer barrier transition (∼2.5 A˚) consistent with earlier work. After tunnel injection of 1017–5×1018electrons/cm2, the barrier undergoes significant degradation leading to enhanced tunneling conductance, with reproducible behavior observed among different samples. This effect is consistent with the generation of positive states in the region of the oxide near the Si/SiO2interface (<20 A˚), where the tunneling electrons emerge into the oxide conduction band. Densities of positive‐charge and interface‐state buildup are also observed from capacitance‐voltage (C‐V) measurements and are found to be consistent with the observed tunneling dependence on positive‐state generation. We suggest that the interface‐state buildup may be identical to the positive‐state generation observed by tunneling. The generated oxide states are shown to anneal slowly at room temperature, and more rapidly at 100 °C. Comparisons are made between wet, wet/annealed, and dry oxidation processes, with wet oxides exhibiting the largest densities of state generation, and dry oxides the smallest. The results are consistent with other work on the effect of water‐related defects in oxides, and with x‐ray photoelectron spectroscopy results, showing that breaking of strained Si‐O‐Si bonds is responsible for state generation during stress. The tunneling data also indicate that, prior to stress, very few positive states reside in the oxide (?1010cm−2), even though appreciable interface‐state desities are observed fromC‐Vdata. We therefore conclude that these initial interface states must be associated primarily with the monolayer transition layer and disorder in the underlying silicon, and are not distributed into the oxide near the interface.

ISSN:0021-8979    

DOI:10.1063/1.329919

出版商:AIP    

年代:1982

数据来源: AIP