The United States of America As Represented by the United States

Rosa T Young

Richard Wood

Jagdish Narayan

Clark W White

Russell D Westbrook

John W Cleland

The invention is a process for producing improved electrical-junction devices. The invention is applicable, for example, to a process in which a light-sensitive electrical-junction device is produced by (1) providing a body of crystalline semiconductor material having a doped surface layer, (2) irradiating the layer with at least one laser pulse to effect melting of the layer, (3) permitting recrystallization of the melted layer, and (4) providing the resulting body with electrical contacts. In accordance with the invention, the fill-factor and open-circuit-voltage parameters of the device are increased by conducting the irradiation with the substrate as a whole at a selected elevated temperature, the temperature being selected to effect a reduction in the rate of the recrystallization but insufficient to effect substantial migration of impurities within the body. In the case of doped silicon substrates, the substrate may be heated to a temperature in the range of from about 200.degree. C. to 500.degree. C.

Modified laser-annealing process for improving the quality of electrical

This invention is a method for improving the electrical properties of silicon semiconductor material. The method comprises irradiating a selected surface layer of the semiconductor material with high-power laser pulses characterized by a special combination of wavelength, energy level, and duration. The combination effects melting of the layer without degrading electrical properties, such as minority-carrier diffusion length. The method is applicable to improving the electrical properties of n- and p-type silicon which is to be doped to form an electrical junction therein. Another important application of the method is the virtually complete removal of doping-induced defects from ion-implanted or diffusion-doped silicon substrates.

Method for making defect-free zone by laser-annealing of doped silicon

This invention is an improved method for preparing p-n junction devices, such as diodes and solar cells. High-quality junctions are prepared by effecting laser-diffusion of a selected dopant into silicon by means of laser pulses having a wavelength of from about 0.3 to 1.1 .mu.m, an energy area density of from about 1.0 to 2.0 J/cm.sup.2, and a duration of from about 20 to 60 nanoseconds. Initially, the dopant is deposited on the silicon as a superficial layer, preferably one having a thickness in the range of from about 50 to 100 A. Depending on the application, the values for the above-mentioned pulse parameters are selected to produce melting of the silicon to depths in the range from about 1000 A to 1 .mu.m. The invention has been used to produce solar cells having a one-sun conversion efficiency of 10.6%, these cells having no antireflective coating or back-surface fields.

Method for forming p-n junctions and solar-cells by laser-beam processing

A NTD semiconductor material comprising polycrystalline silicon having a mean grain size less than 1000 microns and containing phosphorus dispersed uniformly throughout the silicon rather than at the grain boundaries.

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Knoxville, TN, United States of America

Rosa T Young