TECHNOLOGY FOCUS - ELECTRONICS - Preferred Method: In doping the surface region of the semiconductor material, the dielectric material surface layer is provided to perform one or more of the functions of a surface passivation coating, an antireflection coating, or a plating mask. The area to be doped is progressively doped by sequentially locally heating regions within the area to be doped. The heating source is continuously scanned over the surface of the semiconductor material such that the region being heated is continuously moving over the surface, creating a moving melting edge and a molten tail extending from a region of refrozen doped material. Also, the heating source is continuously scanned over the surface of the semiconductor material, such that a currently heated region overlaps previously heated regions where heating one region contributes heat to an adjacent previously heated region, and to which the source is no longer applied, to reduce a rate of cooling of the previously heated region. The heating is applied to discrete regions such that a newly heated region will melt and will also contribute heat to an adjacent previously heated region, and to which the source is no longer applied, to reduce a rate of cooling of the previously heated region. The heating source has a constant output. The intensity of heating is varied over time between a higher level used to initially melt a region and a lower level used to maintain the molten state. The level of heating is decreased after melting a region until the region being heated overlaps an already molten region by less than a predetermined percentage. The region is subjected to refreezing and remelting to achieve required level of doping, where remelting occurs no more than 3 times, and where remelting occurs no more than once. The heating is achieved by scanning one or more a laser beams over the surface of the semiconductor material such that a local region of irradiance by laser beam creates a melted region and scanning the laser over the surface progressively melts a continuous line of surface material. Moreover, a continuous wave (cw) laser is used to heat the surface of the semiconductor material. Heating is achieved by scanning one or more a laser beams over the surface of the semiconductor material such that a local region of irradiance by laser beam creates a melted region and scanning the laser over the surface progressively melts adjacent such regions to form contiguous group of overlapping such regions. The single Q-switched laser is operated in a pulsed operation in which it emits multiple pulses each shorter than a maximum pulse duration of the Q-switched laser with the pulses irradiating overlapping regions of the semiconductor so as to simulate the effects of a cw laser. The repetition period of the pulses is less than 0.02 mu s. The repetition period of the pulses is constant to simulates an output of a constant irradiance cw laser. The scanned beam of the laser is operated at a substantially constant level of irradiance on the surface being heated, and the scanning speed is chosen to melt the surface and to maintain a given point on the surface of the semiconductor material in a molten state for a period of at least 1 microsecond but no more than 10 microseconds. The average irradiance level of one or more laser beams impinging on the surface to locally heat the surface varies with time between at least a high average irradiance level periodically applied for a predetermined time period t1 to cause melting of unmelted semiconductor material on the surface of the semiconductor device within the time period t1 and a lower average irradiance level applied for a further time period t2 after the time period t1 and the lower average irradiance level which maintains melted semiconductor material to remain in a molten state for the time period t2. The cw laser irradiance level is varied cyclically in synchronization with the scanning speed such that the average irradiance level of the laser increases during a melting period and then decreases until the beam has moved over the surface sufficiently for less than a predetermined percentage of the beam to be still exposing molten semiconductor material. The period of the cyclic power variation corresponds to the beam width divided by the scanning speed and the higher output period is 50 % of the cycle or less. During the lower irradiance period t2 the temperature of the molten semiconductor material is kept between 1414 degrees C and 3265 degrees C for at least one microsecond. During the lower irradiance period t2 the temperature of the molten semiconductor material will be kept between 1414 degrees C and 3265 degrees C for 2-10 microseconds. The irradiance level is varied by varying the output power of the laser. The irradiance level is varied by varying the focus of the laser beam to spread the beam during the lower irradiance period t2. A Q-switched laser is used to produce pulses in which the output varies with time such that each pulse has a high irradiance portion and a lower irradiance portion, where variable irradiance is provided using a Q- switched laser which produces output pulses having variable power within the duration of the pulse, a first period of the pulse having a power level which melts irradiated semiconductor material and a second period having an output power that maintains irradiated melted semiconductor material in the molten state. The second period has an output power that does not ablate molten semiconductor material. The variable average irradiance is provided using a single Q-switched laser which is operated in a pulsed operation in which it emits multiple pulses each shorter than a maximum pulse duration of the Q-switched laser with the pulses irradiating overlapping regions of the semiconductor, the repetition period of the pulses being less than 0.02 mu s and the repetition period being varied to simulate a variable output cw laser which produces a cyclic variable output, a higher average irradiance level being produced by providing more closely spaced pulses the cyclic output having an average irradiance level during a first period of each cycle which melts irradiated semiconductor material and an average irradiance level during a second period of each cycle that maintains irradiated melted semiconductor material in the molten state. The second period has an average output irradiance level that does not ablate molten semiconductor material regardless of the period of exposure. Also, the variable irradiance is provided using a cw laser which produces a cyclic variable output having a power level during a first period of each cycle which melts irradiated semiconductor material and a power level during a second period of each cycle that maintains irradiated melted semiconductor material in the molten state. The second period has an output power that does not ablate molten semiconductor material. More than one laser is used to heat the surface of the semiconductor surface, where one laser is used to melt the surface and a second laser is used to maintain the temperature for a period sufficient to allow the dopant to be absorbed. The Q-switched lasers are used to heat the surface. A first, Q-switched laser is used to melt the semiconductor material with a pulse rate and scanning speed selected to allow overlapping exposed areas for consecutive pulses. The pulses of the Q-switched laser are of an intensity where the semiconductor material is melted with a single laser pulse and have a duration of less than 10% of the pulse repetition period. Each laser pulse is overlapped with the previous pulse by 10-50% of the exposure area of the pulses. The second laser is used to ensure that the semiconductor material remains molten between the pulses of the first laser, where the second laser is a cw laser operated with a constant output. The second laser is a Q-switched laser, where the second laser operates to produce output pulses in periods between the pulses of the first laser and at a lower irradiance than the first laser to extend the time during which semiconductor material melted by the first laser remains molten. The second laser is operated in a pulsed operation in which it emits multiple pulses each shorter than a maximum pulse duration of the Q-switched laser with the pulses irradiating overlapping regions of the semiconductor, the repetition period of the pulses being less than 0.02 mu s and the repetition period being constant, to simulate a constant output cw laser at least during the period between the pulses of the first laser. The area to be doped comprises entire surface to create a surface emitter layer; or a part of an entire surface where contacts are to be formed on an illuminated surface of a solar cell. The semiconductor material is silicon. The dielectric layer carries dopant atoms to perform as the dopant source, where the dopant source is a coating located on top of or below the dielectric layer and which carries dopant atoms. Also, the dopant atoms are present in the silicon in an unactivated state to perform as the dopant source where the dopant atoms are absorbed into the silicon structure when the molten silicon crystallizes. The dopant source is in a gaseous state and the heating is performed in an environment containing the gaseous dopant source; or in a liquid state and the heating is performed while the liquid dopant source is applied to the heated surface. The surface of the silicon material is maintained in a molten state for a period which permits substantially uniform distribution of the dopant throughout the molten semiconductor material. The surface of the silicon material is maintained in a molten state for a period which permits all of the molten region to achieve the same overall dopant polarity. In fabricating the multi-layer anti-reflection coating for the solar cell, the semiconductor material structure is based on crystalline silicon semiconductor material. The thermal expansion mismatch correction material is formed before the anti-reflection layer. The front surface region of the semiconductor material structure is passivated by a surface treatment of its light receiving surface before forming the thermal expansion mismatch correction layer, the passivation treatment comprising a dielectric layer surface coating. The front surface passivation treatment comprises forming a thin silicon nitride layer in the range of 10-200 angstrom thick, before forming the thermal expansion mismatch correction layer which comprises a layer of silicon dioxide or silicon oxynitride in the range of 100-300 angstroms thick and the anti-reflection layer which comprises a layer of silicon nitride in the range of 300-800 angstroms. The additional dopant source layer is applied on top of the anti-reflection layer. The additional dopant source layer is formed with a refractive index of approximately 1.5 to optically match a subsequently applied encapsulant material. Also, the additional dopant source layer is removed after a formation of a doped surface region using the dopant of the dopant source layer. The thermal expansion mismatch correction material layer is formed after the anti-reflection layer. The anti-reflection layer comprises a layer of silicon nitride in the range of 300-800 angstroms, and the thermal expansion mismatch correction layer comprises a layer of silicon dioxide or silicon oxynitride in the range of 300 angstroms to 1 micron thick with a refractive index in the range of 1.5-1.6. The thermal expansion mismatch correction layer incorporates dopants and acts as a dopant source during a front surface laser doping process. The thermal expansion mismatch correction layer has a refractive index of approximately 1.5 to optically match a subsequently applied encapsulant material. Preferred Coating: In the multi-layer anti-reflection coating for the solar cell, the semiconductor material structure is based on crystalline silicon semiconductor material. The thermal expansion mismatch correction material is located under the anti-reflection layer. The front surface region of the semiconductor material structure is passivated by a dielectric layer surface coating over its light receiving surface before forming the thermal expansion mismatch correction layer. The front surface passivation layer comprises a thin silicon nitride layer in the range of 10-200 angstrom thick, the thermal expansion mismatch correction layer is located over the passivation layer and comprises a layer of silicon dioxide or silicon oxynitride in the range of 100-300 angstroms thick and the anti-reflection layer is located over the thermal expansion mismatch correction layer and comprises a layer of silicon nitride in the range of 300-800 angstroms. The additional dopant source layer is located over the anti-reflection layer. The additional dopant source layer has a refractive index of approximately 1.5 to optically match a subsequently applied encapsulant material. The thermal expansion mismatch correction material layer is located over the anti-reflection layer. The anti-reflection layer comprises a layer of silicon nitride in the range of 300-800 angstroms, and the thermal expansion mismatch correction layer comprises a layer of silicon dioxide or silicon oxynitride in the range of 300 angstroms to 1 micron thick with a refractive index in the range of 1.5-1.6. The thermal expansion mismatch correction layer incorporates dopants and acts as a dopant source during a front surface laser doping process.The thermal expansion mismatch correction layer has a refractive index of approximately 1.5 to optically match an encapsulant material applied to the solar cell.