Ohmic contacts to n-type and p-type ZnSe

Stable Ohmic contacts are essential for reliable operation of electronic de vices. Such contacts have been made to n-type and p-type ZnSe. Au, Pd, Cu a nd Se for p-type N-doped ZnSe (1 x 10(17) cm(-3)) and AuGe, In, Yb and Mg f or n-type Cl-doped ZnSe (4.5 x 10(18) and 1.15 x 10(19) cm(-3)) grown by mo lecular beam epitaxy (MBE) on (100) semi-insulating GaAs substrates have be en deposited by thermal evaporation. Annealing techniques at different temp eratures, chemical etching and cleaning prior to metallization and reactive ion etching (RIE) in a N-2 plasma and a Ar plasma for p-ZnSe have been stu died. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was deter mined by use of the transmission line method (TLM). The current transport m echanisms for the Mg/Au contact to n-type ZnSe and the Cu/Au contact to p-t ype ZnSe have been studied by the current versus voltage for different temp eratures (I-TI T) measurements. In/Au was best for n-type and Cu/Au for the p-type materials. Plasma treatment of the ZnSe surface prior to metallizat ion was proven to lower the contact resistance to p-type ZnSe. The lowest s pecific contact resistance values of 1.67 x 10(-1) Omega cm(2) for the Cu/A u contact to p-type ZnSe with a N-2 plasma treatment and 1.04 x 10(-2) IZ c m2 for the In/Au contact to n-type ZnSe were achieved. Two different curren t Row mechanisms were shown for the Cu/Au contact to low doped p-ZnSe (1x10 (17) cm(-3)) and three for Mg/Au contact to highly doped n-ZnSe (1.15x10(19 ) cm(-1)). The Cu/Au contact to p-ZnSe and Mg/Au contact to n-ZnSe have bee n observed to be especially stable and reproducible. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.