Photoluminescence and Photoacoustic Spectroscopy of SI Single- and Multi-Step Ingot- and Wafer-Annealed GaAs Crystals
- PDF / 357,336 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 16 Downloads / 198 Views
PHOTOLUMINESCENCE AND PHOTOACOUSTIC SPECTROSCOPY OF SI SINGLEAND MULTI-STEP INGOT- AND WAFER-ANNEALED GaAs CRYSTALS
0. Ka*l, 0. Oda 2 , S. Shigetomi 3 , T. Ikari 4 , Y. Makital, and A. Yamada 1 iElectrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 305, Japan 2 Electronic Materials and Components Research Laboratories, Nippon Mining Co. Ltd, Niizo Minami, Saitama 335, Japan 3 Kurume Univ.,Dep. of Physics, 1635 Mii-machi, Kurume 830, Japan 4 Miyazaki Univ., 1-1 Gakuenkibanadai, Miyazaki 889-21, Japan ABSTRACT SI GaAs crystals submitted to single- or multi-step, ingotor wafer-annealing are investigated using photoluminescence (PL) and photoacoustic spectroscopy (PA). The near-band-edge PL transitions are well resolved, with a neutral acceptor-bound exciton recombination displayed as a split doublet. The improvement induced by wafer-annealing is illustrated by the absence of additional defect-related transitions found after ingot-annealing. For the room temperature PA measurements, the intensity of a peak occuring at 1.39 eV is shown to lead to an estimation of the arsenic micro-defect density as evaluated by AB etching. The 1.39 eV PA band is also asserted to be the nonradiative recombination path of a 1.482 eV band found in the lowtemperature PL spectra. INTRODUCTION Post-growth annealing is usually carried out to improve the structural quality of GaAs crystals to be used as substrates for IC device fabrication. It is highly desirable for the crystals to present low microscopic defect density and uniform cathodoluminescence image, resistivity distribution as well as photoluminescence intensity distribution. It is known that ingotannealing does not fulfill all of the above requirements. This has led to the development of wafer annealing, especially multi1 step wafer-annealing. In a systematic study using photoluminescence and photoacoustic spectroscopy, we have investigated the effects of the different annealing processes on Czochralski-grown GaAs. These studies show the improvement of the quality of wafer-annealed samples and the occurrence of additional defect-related transitions in ingot-annealed crystals. From the photoacoustic measurements, it is concluded that the microscopic defects (arsenic precipitates) are at the origin of the main peak in the spectra. This gives a straightforward method for a quantitative evaluation of these defects. EXPERIMENTAL DETAILS The Czochralski-grown semi-insulating GaAs were supplied by the Nippon Mining Co. Crystals submitted to the different annealing procedures, i.e. singleor multi-step ingot or wafer On leave of absence from Faculty of Science Cheikh Anta Diop University Dakar, Senegal. Mat. Res. Soc. Symp. Proc. Vol. 262. Q1992 Materials Research Society
690
annealing, have been used. The single-step annealing is carried out at 1100 0 C for 5 hours, and the multi-step annealing includes a subsequent treatment at 950 0 C for 5 hours. For wafer processing, 750 pm thick wafers cut from an as-grown ingot are etched and annealed in a quartz ampoule containing arsenic, while the
Data Loading...
