A novel technique for degenerate p-type doping of germanium

J. Sharp, W.J. Lee, K. Ploog, Gilberto A. Umana-Membreno, Lorenzo Faraone, John Dell

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Spin-on dopants offer an expedient, straight forward, and low cost method for doping semiconductors. These sol-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' 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 1020cm-3 which are shown to be fully electrically activated. We report on the use of a traditional "pre-dep"/"drive-in" 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 1 0 0 and n-type 2 1 1 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. © 2013 Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)146-152
JournalSolid-State Electronics
Volume89
DOIs
Publication statusPublished - 2013

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