We report on the dc performance of GaN pup bipolar junction transistors. The structure was grown by metal organic chemical vapor deposition on c-plane sapphire substrates and mesas formed by low damage inductively coupled plasma etching with a Cl-2/Ar chemistry. The de characteristics were measured up to V-BC of 65 V in the common base mode and at temperatures up to 250 degreesC. Under all conditions, I-C-I-E, indicating higher emitter injection efficiency. The offset voltage was less than or equal to 2 V and the devices were operated up to power densities of 40 kW cm(-2). (C) 2002 Elsevier Science Ltd. All rights reserved.