Record Breakdown Voltage (2200 V) of GaN DHFETs on Si With 2- $\mu\hbox{m}$ Buffer Thickness by Local Substrate Removal

In this letter, we present a local substrate removal technology (under the source-to-drain region), reminiscent of through-silicon vias and report on the highest ever achieved breakdown voltage
$(V_{\rm BD})$
of AlGaN/GaN/AlGaN double-heterostructure FETs on a Si (111) substrate with only 2-
$\mu\hbox{m}$
-thick AlGaN buffer. Before local Si removal,
$V_{\rm BD}$
saturates at
$\sim$
700 V at a gate–drain distance
$(L_{\rm GD}) \geq \hbox{8}\ \mu\hbox{m}$
. However, after etching away the substrate locally, we measure a record
$V_{\rm BD}$
of 2200 V for the devices with
$L_{\rm GD} = \hbox{20}\ \mu\hbox{m}$
. Moreover, from Hall measurements, we conclude that the local substrate removal integration approach has no impact on the 2-D electron gas channel properties.