Title :
An AlN/Ultrathin AlGaN/GaN HEMT Structure for Enhancement-Mode Operation Using Selective Etching
Author :
Anderson, Travis J. ; Tadjer, Marko J. ; Mastro, Michael A. ; Hite, Jennifer K. ; Hobart, Karl D. ; Eddy, Charles R., Jr. ; Kub, Francis J.
Author_Institution :
Naval Res. Lab., Washington, DC, USA
Abstract :
A novel device structure incorporating an ultrathin AlGaN barrier layer capped by an AlN layer in the source-drain access regions has been implemented to reliably control threshold voltage in AlGaN/GaN high-electron-mobility transistors. A recessed-gate structure has been used to decrease 2-D electron gas (2DEG) density under the gate, thus controlling threshold voltage while maintaining low on-resistance and high current density. The structure presented in this letter implements an ultrathin AlGaN structure grown by metal-organic chemical vapor deposition capped with AlN to maintain a high 2DEG density in the access regions. A selective wet etch using heated photoresist developer is used to selectively etch the AlN layer in the gate region to the AlGaN barrier. We have demonstrated a repeatable threshold voltage of +0.21 V with 4-nm AlGaN barrier layer thickness.
Keywords :
III-V semiconductors; aluminium compounds; current density; electronic density of states; etching; gallium compounds; high electron mobility transistors; two-dimensional electron gas; wide band gap semiconductors; 2D electron gas density; 2DEG; AlGaN-GaN; AlN; barrier layer thickness; current density; enhancement-mode operation; high-electron-mobility transistors; metal-organic chemical vapor deposition; on-resistance; recessed-gate structure; selective etching; selective wet etching; size 4 nm; source-drain access regions; threshold voltage; ultrathin structure; GaN; high-electron-mobility transistor (HEMT); normally off; wet etch;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2009.2033083
