A technique for p‐n junction formation in silicon, based on deposition of boron on silicon at room temperature followed by laser irradiation is described. Transmission electron microscopy and electrical measurements indicate that as a result of the laser irradiation the boron is dissolved in the silicon and becomes electrically active. Diode characteristics of p‐n junctions produced by this technique are quite good. The dopant profile distribution has been obtained using secondary ion mass spectrometry and is in qualitative agreement with simplified theoretical calculations.

p‐n junction formation in boron‐deposited silicon by laser‐induced diffusion

We have reacted thin Pt, Pd, and Ni films with single‐crystal Si using Q‐switched Nd : YAG laser pulses of 100‐nsec duration in the power range 18–50 MW cm−2. The layers are laterally very uniform in thickness but are not single phase. Average composition of the reaction product layer can be changed over a wide range by varying film thickness and laser power. The microstructure of the reacted layers indicates that reaction occurs via surface melting, mixing, and rapid resolidification.

Laser‐induced reactions of platinum and other metal films with silicon

A technique for solar cell preparation based on vacuum deposition of thin films of dopants on silicon, followed by irradiation with a high‐energy (∼1.5 J/cm2) ruby laser pulse is described. Several dopants like phosphorus, antimony, bismuth, aluminium, gallium, and indium have been investigated. Electrical and Rutherford backscattering measurements indicate that the dopant is dissolved in the silicon and becomes electrically active, as a result of the irradiation. The P‐N junctions which are formed are shallow (depth <4000 A) but heavily doped, since after the laser treatment the solubility of the dopant is generally higher than after a thermal diffusion. Therefore good diode characteristics can be achieved by this simple method, and solar cells up to 14 % efficiency under AM1 (air mass 1) illumination have been realized using dopants like phosphorus, antimony, bismuth, aluminium, or gallium.

Silicon solar cells realized by laser induced diffusion of vacuum‐deposited dopants

The annealing of semiconductors is of critical importance for successful electronic device fabrication. The present review surveys the new field of transient annealing and covers all timescales below those available with the conventional furnace. The work outlined includes the use of techniques which rely upon transient energy deposition in semiconductors from laser, electron beam, ion beam and other radiant sources. The many advances which have been achieved using these transient annealing methods in both fundamental and applied areas of physics are described.

http://iopscience.iop.org/article/10.1088/0034-4885/48/8/002/pdf

Transient annealing of semiconductors by laser, electron beam and radiant heating techniques

The problem of heating a homogeneous slab of material induced by time‐dependent laser irradiance is studied. An exact solution for the temperature distribution of the slab is obtained using the Fourier series expansion technique. The temperatures for the front and rear surfaces are also obtained. The case of time‐independent laser irradiance is considered. The exact expressions for the thermal penetration depth and the critical time required to initiate melting (i.e., damage) are recovered and compared with the published data for this special case.

Heating a slab induced by a time‐dependent laser irradiance—An exact solution

p − n junctions have been prepared by locally alloying a vacuum-evaporated Al film into n -type Si with a focused heat pulse derived form a Nd:YAG laser. The preparation and the gross features of such junctions are described and electrical measurements of the forward bias and reverse bias current, reverse bias capacitance and transient response are given for room temperature. The forward and reverse bias current measurement show that charge recombination and generation within the depletion region controls the flow of current as would be expected for a Si junction. The reverse bias capacitance shows that the change in the doping profile in these junctions is abrupt. From the transient response the reverse recovery time is typically 0.5 × 10 −9 sec.

M.I. Cohen

Papers

Properties of Si diodes prepared by alloying Al into n-type Si with heat pulses from a Nd:YAG laser

Properties of Si diodes prepared by alloying Al into n-type Si with heat pulses from a Nd:YAG laser