Characteristics of Ohmic Contacts to n-Type Boron Phosphide

We grew n-type boron phosphide (BP) (100) on a p-type Si(100) substrate by hydride vapor phase epitaxy. Electrical contacts are important for electrical evaluations and device applications, but the resistivity of ohmic contacts to BP has been little studied. We evaluated the contact characteristics...

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Bibliographic Details
Published inJapanese Journal of Applied Physics Vol. 52; no. 3; pp. 031201 - 031201-8
Main Authors Ino, Yuji, Nishimura, Suzuka, Hirai, Muneyuki, Matsumoto, Satoru, Terashima, Kazutaka
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.03.2013
Subjects
Aluminum
Annealing
Boron phosphides
Contact resistance
Devices
Gold
Ohmic
Titanium
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Summary:We grew n-type boron phosphide (BP) (100) on a p-type Si(100) substrate by hydride vapor phase epitaxy. Electrical contacts are important for electrical evaluations and device applications, but the resistivity of ohmic contacts to BP has been little studied. We evaluated the contact characteristics for Al, Au, In, Ti, and Pt by annealing at temperatures in the range 300--500 °C for annealing times up to 50 min using a circular transmission line model pattern. Ohmic characteristics were obtained for the Al, Au, In, and Ti contacts. For the ohmic samples, we calculated the specific contact resistance $\rho_{\text{c}}$ and observed a metal--BP interface by cross-sectional transmission electron microscopy. The minimum specific contact resistance $\rho_{\text{c}}$ was $2\times 10^{-5}$ $\Omega$ cm 2 for the Au/In/n-BP sample annealed at 500 °C for 50 min. For the present samples, thermionic-field emission is considered to be the dominant carrier transport process across the metal--BP interface.
Bibliography:Plan view of CTLM pattern. The metal in the gap region was removed by wet etching. Relation between annealing temperature and carrier concentration in BP annealed for 10 (solid line) and 50 min (broken line). SEM images of BP surfaces (a) unannealed and annealed at (b) 300, (c) 400, (d) 500, (e) 600, and (f) 700 °C for 50 min. Typical result for $I$--$V$ measurement performed for three CTLM patterns of the Al contacts (a) before annealing ($R_{\text{ave}} = 145$ $\Omega$ and $r^{2} = 0.947$) and (b) annealed at 500 °C for 30 min ($R_{\text{ave}} = 18.1$ $\Omega$ and $r^{2} = 1.000$). Resistance $R_{\text{ave}}$ (left axis, solid lines) and linearity of $I$--$V$ curve $r^{2}$ (right axis, dotted lines) for various times and annealing temperatures for (a) Al, (b) Au, (c) Au/In, (d) Ti, and (e) Pt contacts. Specific contact resistance $\rho_{\text{c}}$ plotted against annealing time and temperature. XTEM images of (a) Al, (b) Au, and (c) Ti contacts annealed at 500 °C and their enlarged images [(d)--(f)]. Plot of $\ln \rho_{\text{c}}$ in Fig. against the metal electronegativities $X_{\text{M}}$ given in Refs. and .
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ISSN:0021-4922
1347-4065
DOI:10.7567/JJAP.52.031201