Production of Electronically Excited P 2 and in from ArF Excimer Laser Irradiation of InP
- PDF / 787,027 Bytes
- 8 Pages / 417.6 x 639 pts Page_size
- 61 Downloads / 173 Views
PRODUCTION OF ELECTRONICALLY EXCITED P2 AND In FROM ArF EXCIMER LASER IRRADIATION OF InP V. M. DONNELLY, V. R. McCRARY AND D. BRASEN, AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey 07974
ABSTRACT We have investigated the decomposition of single-crystal InP surfaces irradiated by a 193 nm ArF excimer laser. These studies provide insight into mechanisms of thermal decomposition, surface diffusion and epitaxy. Pulsed laser exposure leads to evolution of P 2 from the surface which is detected by resonance fluorescence resulting from a fortuitous overlap of the C';+,, v' - 11 - X'2,+ v"-0 with the laser frequency. P2 -evolution occurs above a threshold fluence of 0.12 J/cm 2 and lags the peak laser intensity by -20 nsec. These observations are explained by a thermally activated decomposition mechanism, as opposed to any direct, photochemical ejection process. Peak surface temperatures have been calculated and are used to predict P2 yields as a function of fluence and time which are in good agreement with experiments. These findings are also discussed in relation to previous studies of excimer laser stimulated growth of InP.
1. INTRODUCTION Recently, we demonstrated the growth of epitaxial InP films at very low substrate temperatures by using a 193 nm ArF excimer laser to photodissociate organometallic precursor compounds [1]. The laser was directed through a volume of deposition and carrier gases, which absorbed some fraction of the light. The transmitted beam, which irradiated the depositing film at normal incidence, stimulated removal of carbon-containing impurity species and promoted epitaxy by a laser-annealing process. We also observed that continued laser irradiation of the film with no deposition gases present produced optical emission from electronically excited P 2 and In [2]. In the present study, we have extended these observations to single crystal (100) InP surfaces, and have observed both time-averaged and time-resolved emission as a function of laser fluence, irradiation time, laser repetition rate, and substrate temperature. These studies provide insight into UV-laser induced surface decomposition, diffusion, crystallization and epitaxy.
A more detailed account of this work,
including studies of other crystal orientations, is published elsewhere [3].
2. EXPERIMENTAL The apparatus consists of a stainless steel deposition chamber, excimer laser (Questek model 2860), and double monochromator (ISA model U1000) spectrometer system 14-5]. Optical emission emanating from a region within 1 mm of the surface is collected at an angle of -4° with respect to the surface plane with a 25 cm focal length fused silica lens and imaged onto the entrance slit of the double monochromator. Single-pulse, spectrally-resolved fluorescence is detected with a photomultiplier tube (RCA C31034) and boxcar integrator, and the data are stored on the computer. The output of the photomultiplier tube is broadened to -1 Msec with a 10 Kf1 load resistor, and integrated with a 10 psec wide gate to capture the ent
Data Loading...
