Monocrystal Dislocationless Si:Ge, Grown From the Melt with Gd Impurity.
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MONOCRYSTAL DISLOCATIONLESS Si :Ge, GROWN FROM THE MELT WITH Gd IMPURITY.
Borschensky V.V., Brinkevich D.I., Petrov V.V., Prosolovch V.S. Byeloruassian State University, Department of Physic, Soorina Avenue, 4, 220080 Minsk, Republic Belarus. ABSTRACT
The properties of Si grown from the melt having impurities of germanium and gadolinium have been studied by IR-absorption and Hall effect methods.It was stated that Ge and Gd are effective getters for technological impurities of oxygen and carbon in silicon melt. It has been shown that the combined doping by rare earth and isovalent impurities allows to increase the thermostability of dislocationless monocrystals of silicon. 1.INTRODUCTION It is known that doping of silicon by rare earth elements (REE) increases its thermal and radiation stability [1]. It has been stated earlier that isovalent impurity (IVI) Ge in silicon suppresses generation of thermodonors (TD) introduced at 450 0O [2], but practically does not effect the formation of high temperature thermal donors (HTTD) [3]. Thus the study of the properties of silicon doped simultaneously by the REE and IVI impurities is of great interest. 2. E(PERIMenTAL ASPECTS
In this paper dislocationless n-Si monocrystals grown from the melt involving Ge and Gd impurities by Czochralsky method have been studied. Their resistivity was ~ 10 Ohm.cm. Concentrations of IVI (Nce) and REE (NGd) were measured by the method of neutron-activated analyses.Note that NGd in all samples was -< 1013 cm-3,i.e. beyond the limits of detection. Concentration of the interstitial oxygen and carbon in the state of reMat. Res. Soc. Symp. Proc. Vol. 301. @1993 Materials Research Society
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placement was found by the IR bands of absorption at 1106 and 607 cm- 1 using empirical coefficient of 3,3.1017 and 2,2.1017 cmcorrespondingly. Measurements of Hall effect and conductivity were made in the temperature range of 77-300 K. Thermal treatment (TT) have been made in air at 450 and 650 00 for period to 100 hours. 3. RESULTS AND DISCUSSIONS.
A.Gettering The results of measurements (Table 1) show that Ge and Gd are getters for oxygen and carbon in the melt and this effect is the most prominent for the latter technological impurity. The noticeable decreases of oxygen concentration in the doped REE and IVI samples were observed only for the lower parts of the ingots. It should be noted that the simultaneous introducing of Ge and Gd into the melt efficiently increased the rate of purifying of monocrystals from C. Gettering effect Table 1. Original parameters of silicon ingots. Ingots
Test material
Si:Ge
Si:Gd
Si:Ge,Gd
Number of the wafer 1u 1P
1L 2U 2P 2L
14 , NGe.10 2 0 , N. 10 17 , NO1016, ND Ge-3 0,-3 C*-3 -D103 cm cm cm cm-
-
8,6 6,5
6,7 16,0
-
8,3
42,2
8,7 6,3 7,8
,0 13,5 35,3
0,
8,6 6,4 7,6
5,3 7,4 13,2
0,2 -
8,5 6,5 7,1
3,3 5,0 7,5
0,2 -
-
1,6E 1,14 1,27
3U 3P
-
3L
-
4U 4P 4L
-
0,80 0,87 0,94
1,53 -
-
-
-
(* U,P,L- upper part, middle part, lower part of the ingot, NGTD)- concentration of "grown" thermodonors
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