A finite element simulation was used to quantitatively estimate the effectiveness of flip-chip bonding in the temperature rise of bulk GaN Schottky rectifiers under various conditions of current density, duty cycle, forward turn-on voltage and on-state resistance. The temperature difference between flip-chip bonded devices and bottom bonded devices was 20 degreesC even at modest current densities. The maximum temperature in the bulk cases occurred in the center of the GaN substrate thickness. The transit time of the temperature reaching the steady state for the flip-chip bonding device is in the range of millisecond, which is faster than that of most power switch applications. Flip-chip bonding is suggested to improve the heat dissipation of high power, bulk GaN rectifiers. (C) 2003 Elsevier Science Ltd. All rights reserved.