In Al N ∕ Ga N metal-oxide-semiconductor high electron mobility transistor with Al2O3 insulating films grown by metal organic chemical vapor deposition using Ar and NH3 carrier gases

Abstract

Al 2 O 3 thin films were deposited by a metal organic chemical vapour deposition on InAlN∕GaN heterostructures using Ar or NH3 as a carrier gas. Effects of NH3 and Ar carrier gases on the electrical and structural properties of Al2O3∕InAlN∕GaN HEMT devices were investigated by current voltage, current collapse, and Auger electron spectroscopy measurements. Al2O3 deposited using Ar as a carrier gas leads to a substantial gate leakage current reduction with no increase of the current collapse compare to Schottky gate based HEMT. On the other hand, HEMT electrical performance shows degradation if NH3 carrier gas is used. Similarly, Auger electron spectroscopy revealed presence of carbon on InAlN surface when NH3 carrier gas was applied. It is suggested that the formation of carbon-related traps on the InAlN surface takes place in the early stages of the Al2O3 deposition with NH3 carrier gas that strongly influences the HEMT performance.

Positive Threshold-Voltage Shift of Y2O3Gate Dielectric InAlN/GaN-on-Si (111) MOSHEMTs with Respect to HEMTs

“…3 that the magnitude of V th for all MOSHEMTs with various Y 2 O 3 thicknesses from 5-30 nm is less negative than that of Ni/W Schottky gate HEMTs (V th ∼ -1.45 V). This is in contrast to MOSHEMTs with a 10 nm ZrO 2 gate dielectric, which have a much larger negative V th (∼ -7.5 V) compared to Ni/W Schottky gate HEMTs, and this is the commonly observed trend owing to a lower gate capacitance (as a result of increased gate-to-channel separation), positive interface and bulk charges, and the presence of dipoles at the oxide/substrate interface [12][13][14][15][16] for MOSHEMTs. Although the gate metals in our MOSHEMTs and HEMTs are different (i.e., W versus Ni/W), we do not anticipate the opposite V th shifts observed for Y 2 O 3 and ZrO 2 gate dielectric MOSHEMTs with respect to HEMTs to be changed if the gate metal of HEMT is changed to W and this is explained as follows.…”

“…As seen in Table I, both n ox,intf and n ox,bulk are negative, which are in contrast to commonly observed positive fixed oxide charges for MOSHEMTs with other gate dielectrics such as Al 2 O 3 , HfO 2 , ZrO 2 etc. [12][13][14][15][16] Since both negative n ox,intf and n ox,bulk will shift V th toward positive value, we believe this is the reason for the positive V th shift observed in our Y 2 O 3 gate dielectric InAlN/GaN MOSHEMTs with respect to Schottky gate HEMTs, as shown in Fig. 3.…”

“…Several high-k gate dielectrics, e.g., HfO 2 , ZrO 2 , GdScO 3 , Ga 2 O 3, etc have been investigated earlier in InAlN/GaN MOSHEMTs and have demonstrated improved electrical characteristics compared to those for Schottky gate HEMTs. [12][13][14][15][16] However, in spite of a large bandgap (∼5.5 eV), high-k value (k∼12-18), and large conduction z E-mail: elemkb@nus.edu.sg; elecef@nus.edu.sg band offset, rare-earth based high-k dielectric such as Yttrium oxide (Y 2 O 3 ) has not been explored to date as a gate dielectric in GaN-based MOSHEMTs. [17][18][19] Presently, high quality 4 inch InAlN/GaN-on-Si wafers are available commercially and with gold-free contacts, they can be processed in existing Si foundries, hence further reducing the cost of InAlN/GaN transistors.…”

Suppression of Gate Leakage and Enhancement of Breakdown Voltage Using Thermally Oxidized Al Layer as Gate Dielectric for AlGaN/GaN Metal–Oxide–Semiconductor High-Electron-Mobility Transistors

“…Among the insulators available Al 2 O 3 is promising due to its large band gap and high dielectric constant ($9). Several researchers have demonstrated the growth of Al 2 O 3 on AlGaN/GaN surface by conventional techniques like liquid phase deposition (LPD), 1) atomic layer deposition (ALD) 2) and metal-organic chemical vapor deposition (MOCVD) 3) for AlGaN/GaN MOS-HEMT. Few studies were made to convert Al layer into its respective oxide before gate metallization for AlGaN/GaN HEMT.…”

Control of plasma-CVD SiO2/InAlN interface by ultrathin atomic-layer-deposited Al2O3interlayer

“…11,12) To solve this problem, the construction of a metal-insulator-semiconductor (MIS) gate structure has been proposed for InAlN/GaN HEMT applications. 11) Thus far, combinations of InAlN and several insulators, including Al 2 O 3 , 11,[13][14][15][16][17] ZrO 2 , 14,18,19) GdScO 3 , 14) HfO 2 , 18) SiO 2 , 20) plasma oxides, [21][22][23][24][25] and thermal oxides, 26,27) have been used to construct MIS gate structures to reduce the leakage current. Among these insulators, SiO 2 is attractive because it has the largest band gap among the insulators in practical use.…”