Luminescence Due to Mn Doped GaP
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LUMINESCENCE DUE TO Mn DOPED GaP TERESA MONTEIRO AND ESTELA PEREIRA Departamento e Centro de Fisica (INIC),
Universidade de Aveiro, Portugal
ABSTRACT 2 In n-type GaP doping with Mn gives rise to a deep centre due to Mn+ . Its luminescence occurs in the near infrared. The behaviour of this centre is studied as a function of temperature and the thermal quenching of the luminescence interpreted as due to a non-radiative process to the ground state. The behaviour of another band that appears upon doping with Mn is also discussed.
INTRODUCTION The growing interest in III - V compounds have rendered important the knowledge of the effect of the presence of transition metals in these crystals. GaP is the only III - V material where Mn originates a deep centre due to Mn+ 2 . The luminescence and EPR spectra of this centre is known [1,2]. Mn is the trasition metal with higher solubility in GaP (ca. 10-1 9 cm 3 ), but has a small diffusion coefficient. Therefore it is easier to obtain Mn doped samples by an in-growing process than by diffusion into the crystal. The Mn+ 2 luminescence occurs in the near infrared and is due to a 4Tl -0.Al transition. A splitting of the hT1 level of 9.5 meV is observed with an identical transition probability to the ground state as shown by the temperature behaviour of the two corresponding ZPL, and the corresponding lifetime of the luminescence up to 77 K [1]. In order to get a more detailed knowledge about the Mn+ 2 luminescence in GaP we studied the behaviour of this luminescence as a function of temperature and time. In all Mn doped samples an extra unstructured luminesis observed although its intensity cence band (red band) at higher energies 2 intensity. The luminescence excitation does not correlate with the Mn+ spectra of the two bands is also different for excitation within the band gap although for both the more efficient process of excitation is above band gap. EXPERIMENTAL DETAILS The samples used in this work were of two different origines: in one Mn has been grow-in in the presence of excess of donnors (mainly sulphur) with a Mn concentration of 10-5 g/g, in the others n-type LEC grown GaP (sulphur and carbon present) has been doped by vapour deposition of Mn followed by diffusion in an evacuated quartz ampoule 23h at 1100 0 C, giving a lower Mn concentration. Time resolved luminescence spectra and lifetime measurements were carried out with a Spex 1934C phosphorimeter; luminescence excitation was observed using a W-lamp. Steady state spectra were measured using an Ar-Laser as excitation source. The samples were held in the cold tip of a closed cycle He cryostat. EXPERIMENTAL RESULTS In Fig. 1 the steady state is shown.
luminescence of a Mn doped GaP sample
Mat. Res. Soc. Symp. Proc. Vol. 163. '1990 Materials Research Society
216
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Uncorrected luminescence spectrum of Mn doped sample at 11 K, excited by the 488 nm Ar laser line. Insert: luminescence specof Mn+ 2 .
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