LPE Growth of Doped SiGe Layers Using Multicomponent Phase Diagrams Calculations
- PDF / 1,253,636 Bytes
- 11 Pages / 420.48 x 639 pts Page_size
- 49 Downloads / 203 Views
LPE GROWTH OF DOPED SiGe LAYERS USING MULTICOMPONENT PHASE DIAGRAMS CALCULATIONS J.-P. FLEURIAL, A. BORSHCHEVSKY and D. IRVINE Jet Propulsion Laboratory/ California Institute of Technology CA 91109 Pasadena, 4800 Oak Grove Drive,
ABSTRACT Heavy doping of n-type Si-Ge alloys is necessary for improving Because of properties. their high temperature thermoelectric the limited solid solubility of the best dopant available, gallium were started simultaneous additions of phosphorus, several years ago. The substantially higher carrier concentration such super-saturated, hot-pressed SiGe/GaP values obtained in solid dopant in changes significant to point materials solubilities. To better understand the behavior of these alloys, investigation of homogeneous single crystalline materials were As a near-thermodynamic equilibrium technique with needed. processing temperatures well below the melting point of these liquid-phase epitaxy (LPE) was particularly suited to materials, Based on successful the study of the mechanisms of multidoping. crystal growth of Si 1 _xGex thin films using metals such as Ga, In, several experiments were designed to Sn and Bi for solvents, grow multi-doped SiGe layers with III-V dopant combinations. Knowledge of ternary and quaternary phase diagrams is essential systems Si-Ge-M Ternary process. the LPE to develop computations in good agreement with experimental determinations multicomponent were used to calculate some of the necessary phase diagrams and assess the strength of the various III-V interactions.
INTRODUCTION Hot-pressed Si-Ge alloys have been widely used as high temperature thermoelectric material for space applications [1) and any improvements in the thermoelectric energy conversion Efforts to efficiency of these alloys are highly desired. improve this efficiency in n-type Si 8 0Ge 20 focused primarily on increasing the carrier concentration as doping levels as high as Several years for p-type materials could not be achieved [2,3]. ago, serious consideration was given to additions of Ga to the P used as dopant, and it was found recently that (Ga+P)-doped hotpressed Si8Ge 20 samples could achieve 20 to 30% improvement over Work was started standard P-doped only Si 80Ge 20 materials [4,5]. order to understand the mechanisms involved when doping in However, because of simultaneously with III and V dopants [6]. hot-pressed material inhomogeneity and grain boundaries, it was difficult to satisfactorily relate the thermal and electronic properties of Si-Ge alloys to their structure and composition. Homogeneous single crystalline materials are needed to better understand and characterize these improvements, as the unknown contribution of grain boundaries is eliminated and doping level is under good control.
Mat. Res. Soc. Symp. Proc. Vol. 234. 01991 Materials Research Society
124
To study the changes in dopant solid solubility with Si-Ge alloys composition and for various doping combinations, growth of doped Sil.xGex thin films was started at the JPL using LPE. As a near-thermodynamic equi
Data Loading...
