科研之友
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摘要
Spin-on dopants offer an expedient, straight forward, and low cost method for doping semiconductors. These sal-gel dopant films contain sufficient impurity content to obtain surface concentrations well above the solubility limit of most semiconductors (e.g., Si, Ge). While much has been published about spin-on dopants for degenerate doping of Si, there is to the authors%26apos; knowledge no report in the literature of such films being used to achieve degenerate p-type doping of Ge, as there are a number of technical challenges associated with this technique. In this work, we present a novel technique for degenerate p-type doping of Ge using Ga spin-on dopant films in a regular horizontal tube furnace. This technique gives both excellent uniformity, higher doping concentrations and better potential for ultra-shallow junctions than diffusion from solid sources, is much preferred to rapid melt/alloyed junctions (especially for optoelectronic applications), and is readily applicable to rapid thermal processing. In this preliminary investigation, we report doping concentrations exceeding 10(20) cm(-3) which are shown to be fully electrically activated. We report on the use of a traditional %26quot;pre-dep%26quot;/%26quot;drive-in%26quot; approach, which could be used to give shallow dopant profiles, or tailored dopant concentrations, for a wide variety of electronic and optoelectronic applications, and to form back surface fields in photovoltaic and thermo-photovoltaic devices. Values of 3.4 +/- 0.2 eV and 3.2 +/- 0.4 eV are extracted for the activation enthalpies of the diffusion processes into p-type %26lt; 100 %26gt; and n-type %26lt; 211 %26gt; Ge substrates, respectively, which are shown to be in good agreement with previously published data [1,2]. We conclude that Ga is a more suitable dopant for reliable, low-cost, degenerate p-type doping of Ge, rather than B (also investigated in this work), which is known to be problematic.
- 出版日期2013-11
