Alok K. Berry

Transition metal implants in In0.53Ga0.47As

Single‐ and multiple‐energy Fe, Cr, and V ions were implanted into InGaAs. Annealing of the implanted InGaAs samples caused a redistribution of the implanted atoms, as determined by secondary ion mass spectrometry. Coimplantation of Fe with P did not prevent this redistribution. A transport equation calculation of Fe‐implantation‐induced stoichiometric disturbances in InGaAs was done. The lattice quality of implanted InGaAs was investigated by photoreflectance measurements. Fe‐implanted InGaAs has a resistivity close to the intrinsic limit, whereas Cr‐ and V‐implanted InGaAs have a lower resistivity than the unimplanted material.

Photoluminescence and Raman studies of CdS films grown by metal-organic chemical vapor deposition on Si{111} substrates

Abstract CdS epitaxial films grown using metal-organic chemical vapor deposition on Si{111} substrates at growth temperatures ranging from 270 to 325 °C have been characterized using photoluminescence and Raman spectroscopy. Out of all the samples the best optical behavior is obtained from that grown at the lowest temperature. Samples grown at the lowest temperature exhibited increased intensity of the bound excitonic peaks and reduced emission at the defect-related luminescence region. The Raman spectra were compatible with the film surface being normal to the c axis, indicating a preferred growth orientation.

Photoreflectance of semi‐insulating InP: Resistivity effects on the exciton phase

It is shown that photoreflectance (PR), a contactless form of modulation spectroscopy, can be used to measure the resistivity of semi‐insulating InP:Fe substrates. PR measurements of the substrates, obtained from various vendors and laboratories, were performed at 82 K and had line shapes dominated by excitonic transitions. The phase angle of the line shape was found to be a measure of the bulk resistivity of the substrate. The behavior of the line shape phase angle is explained by the exciton ionization model, where the electric field near the surface of the sample is sufficient to ionize excitons. The extent of this ionizing electric field corresponds to an optical path length which enters additively into the exciton line shape phase. Samples with higher resistivities have ionizing electric fields of larger extent, increasing the phase angle of the exciton line shape.

Be, S, Si, and Ne ion implantation in InSb grown on GaAs

Single‐ and multiple‐energy Be, S, Si, and Ne ion implantations were performed at room temperature in InSb grown on semi‐insulating GaAs substrates. The implanted material was subjected to both isochronal and isothermal annealing schemes. The as‐implanted and annealed material was characterized by Hall, secondary ion mass spectrometry, and x‐ray rocking curve measurements. The as‐implanted material is highly n‐type for all implant species used in this study. A maximum p‐type activation of 90% and n‐type activation of 16% was achieved for Be and S implants, respectively. Be activation depends on the thickness of the InSb layer. No in‐diffusion of Be and S was observed even after 500 °C anneal. The Si implant has an amphoteric doping behavior.

B implants in Si1−xGex/Si

Boron ion implantations were performed into 100 nm thick, undoped, strained Si1−xGex alloy films with x values of 0, 0.1, and 0.2 grown on (100) Si. B implants of 1×1013, 1×1014, and 1×1015 cm−2 were done at 20 keV. Implant activation was accomplished by using either 20 s rapid thermal anneals or 10 min furnace anneals, both at temperatures up to 800 °C. The annealed material was characterized by Hall, secondary ion mass spectrometry, and x‐ray rocking curve measurements. We observed an increasing B activation with increasing Ge concentration in the alloy. For x=0.2 we obtained 100% B activation for 1×1013 and 1×1014 cm−2 implants annealed at 700 and 800 °C.

Si-implantation into GaAs grown in Si

Abstract200 keV Si implantations were performed in the dose range of 5 × 1012 − 1 × 1014 cm−2 in GaAs grown on Si. For comparison implants were also performed in GaAs layers grown on GaAs substrates. Implanted layers were annealed by both furnace and halogen lamp rapid thermal anneals. Significantly lower donor activations were observed in GaAs layers grown on Si substrates than in the layers grown on GaAs substrates. Extremely low dopant activations were obtained for Be implants in GaAs grown on Si. Photoluminescence and photoreflectance measurements were also performed on the implanted material.

S and Si ion implantation in GaSb grown on GaAs

Single and multiple energy S and Si ion implantations were performed at room temperature (RT) and 200 °C into GaSb epitaxial layers grown on semi-insulating GaAs substrates. The implanted material was annealed with a Si3N4 cap at 400–600 °C for 5 min. Secondary ion mass spectrometry measurements indicated the thermal stability of the Si and S implants even for 600 °C annealing. Appreciable donor electrical activations of Si and S were obtained only for 200 °C implantation for annealing temperatures ⩾500 °C. For S implantation the calculated substitutional activation is ∼50%. Rutherford backscattering/channeling measurements indicated a lattice quality that is close to the virgin level for samples annealed at 600 °C. N-type conduction was not observed in GaSb bulk material implanted at either RT or 200 °C.

Doping studies of spray-deposited CdTe films

Abstract The results of doping spray-deposited cadmium telluride films on glass substrates are reported. The films were 1–4 μm thick, displayed excellent adhesion to the substrate and possessed good surface morphology. The doping was achieved by incorporating the dopant source into the spraying solution. The films doped with indium and sodium show a decrease in resistivity by a factor of 100 with respect to the resistivity of undoped films grown under similar conditions. Attempts to dope with caesium and phosphorus were not satisfactory. Transport measurements were performed and they were found to be influenced significantly by the built-in potential at the grain boundaries.

Growth of CdTe and CdS/CdTe heterojunctions on metal substrates by spray pyrolysis

Abstract Preliminary results of the spray pyrolysis of thin films of CdTe on metal substrates are reported. The films are hard and adhere well to the substrate. A n-CdS/p-CdTe rectifying junction is also grown completely by spray pyrolysis on the metallic substrate. The ability to produce p-n junctions using the inexpensive and simple procedure of spray pyrolysis may lead to a viable process for mass production of solar cells.

Photoluminescence and Raman scattering characterization of As-grown and implanted bulk ZnSe crystals

As-grown bulk ZnSe material prepared by seeded physical vapor transport (SPVT) and melt- grown techniques, and N ion-implanted and heat-treated SPVT material are characterized by room-temperature Raman scattering and low-temperature photoluminescence techniques to evaluate the lattice perfection and to find the impurity and defect levels in the material. The measurements have indicated that the SPVT material is of better quality compared to the melt- grown material. The 200 keV/5 X 1013 cm-2 N ion-implantation and 650 degree(s)C/10 min anneal have resulted in high intensity deep energy level peaks in the photoluminescence spectra recorded on the SPVT samples.