Temperature dependence of electrical properties in Be-implanted semi-insulating GaAs

Abstract

The Hall coefficient and sheet resistivity have been measured as functions of temperature for Cr‐doped semi‐insulating GaAs implanted with 100‐keV Be ions at fluences between 1×10¹³ and 5×10¹⁵ cm⁻². Impurity conduction influences or dominates hole transport processes at all temperatures for fluences of 1×10¹⁴, 4×10¹⁴, and 5×10¹⁵ cm⁻², but is evident only for T 13 and 4×10¹³ cm⁻². Analysis of higher‐temperature sheet‐hole concentration data for these lower‐fluence implants indicates the implanted layers are heavily doped and compensated, and the activation energy E_a decreases with increasing ionized acceptor concentration N_ai. These results, along with an earlier result for a much lower concentration of implanted Be acceptors, can be represented by E_a=28.4 meV −(1.77×10⁻⁵) N^1/3_ai. In addition, measurement of electrical properties as a function of room‐temperature sample‐storage time indicates slow activation of compensating donors for the 4×10¹³‐cm⁻² implant. This effect is not observed for 4×10¹⁴‐ and 5×10¹⁵‐cm⁻² implants.