Breakdown Enhancement of AlGaN/GaN HEMTs on 4-in Silicon by Improving the GaN Quality on Thick Buffer Layers

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We have achieved a 9- <formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula>-thick AlGaN/GaN high-electron mobility transistor (HEMT) epilayer on silicon using thick buffer layers with reduced dislocation density <formula formulatype="inline"><tex Notation="TeX">$(D_{D})$</tex></formula>. The crack-free 9- <formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula>-thick epilayer included 2- <formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> i-GaN and 7- <formula formulatype="inline"><tex Notation="TeX">$ \mu\hbox{m}$</tex></formula> buffer. The HEMTs fabricated on these devices showed a maximum drain–current density of 625 mA/mm, transconductance of 190 mS/mm, and a high three-terminal OFF breakdown of 403 V for device dimensions of <formula formulatype="inline"><tex Notation="TeX">$L_{g}/W_{g}/L_{\rm gd} = \hbox{1.5/15/3} \ \mu\hbox{m}$</tex> </formula>. Without using a gate field plate, this is the highest <formula formulatype="inline"><tex Notation="TeX">$BV$</tex> </formula> reported on an AlGaN/GaN HEMT on silicon for a short <formula formulatype="inline"><tex Notation="TeX">$L_{\rm gd}$</tex> </formula> of 3 <formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula>. A very high <formula formulatype="inline"><tex Notation="TeX">$BV$</tex></formula> of 1813 V across 10- <formula formulatype="inline"><tex Notation="TeX">$\mu \hbox{m}$</tex></formula> ohmic gap was achieved for i-GaN grown on thick buffers. As the thickness of buffer layers increased, the decreased <formula formulatype="inline"><tex Notation="TeX">$D_{D}$</tex></formula> of GaN and increased resistance between surface electrode and substrate yielded a high breakdown. </para>