GaAs metal-oxide-semiconductor devices with a complex gate oxide composed of SiO<sub>2</sub>and GaAs oxide grown using a photoelectrochemical oxidation method

Applied Physics Letters

Stoklas

et al. 2012

Application of GaAs-based metal-oxide-semiconductor (MOS) structures, as a “high carrier mobility” alternative to conventional Si MOS transistors, is still hindered due to difficulties in their preparation with low surface/interface defect states. Here, aluminum oxide as a passivation and gate insulator was formed by room temperature oxidation of a thin Al layer prepared in situ by metal-organic chemical vapor deposition. The GaAs-based MOS structures yielded two-times higher sheet charge density and saturation drain current, i.e., up to 4 × 1012 cm−2 and 480 mA/mm, respectively, than the counterparts without an oxide surface layer. The highest electron mobility in transistor channel was found to be 6050 cm2/V s. Capacitance measurements, performed in the range from 1 kHz to 1 MHz, showed their negligible frequency dispersion. All these results indicate an efficient suppression of the defect states by in situ preparation of the semiconductor structure and aluminum oxide used as a passivation and gate insulator.

mentioning

confidence: 99%

Aluminum oxide as passivation and gate insulator in GaAs-based field-effect transistors prepared in situ by metal-organic vapor deposition

Applied Physics Letters

Stoklas

et al. 2012

“…Therefore, the realization of effective MOS structures was hindered. However, recent studies show that an application of suitable gate insulator and passivation allows us to suppress the density of defects, as reported on MOS capacitors and heterostructure field-effect transistors (MOSHFETs) [4][5][6][7][8][9][10][11][12][13][14][15]. Description 'III-V based MOS' is usually used for devices with an InGaAs channel, in contradiction to GaN channel devices.…”

Section: Introductionmentioning

confidence: 99%

“…Mostly these methods are applied in the form of an ex situ process, i.e. the device structure is contacted with air before an insulator is deposited [4][5][6][7][8][9][10]. Such a procedure enables us to create uncontrollable high density of interfacial defect states which might cause a degradation 0268-1242/12/115002+05$33.00 of the MOS device performance.…”

Section: Introductionmentioning

confidence: 99%

GaAs-based metal-oxide-semiconductor field-effect transistor with aluminum oxide gate insulator preparedin situby MOCVD

Fox

Semicond. Sci. Technol.

et al. 2012

Preparation and properties of GaAs-based metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) are described. Aluminum oxide as a passivation and gate insulator was formed by room temperature oxidation of a thin Al layer deposited in situ on top of the InGaAs-channel/GaAs-substrate layer structure by metal-organic CVD (MOCVD). The devices yielded a maximum drain current of 480 mA mm −1 and a peak extrinsic transconductance of 147 mS mm −1 . The devices exhibited negligible capacitance dispersion with frequency, which indicates low density of trap states in the structures prepared. From the microwave measurements, extracted current gain and unilateral power gain cutoff frequencies were 19 and 48 GHz, respectively, on devices with 1.5 μm gate length. Device modeling based on measured small signal S-parameters shows that the transconductance is predominantly responsible for an enhancement of the MOSHFET microwave performance.

III-As heterostructure field-effect transistors with recessed ex-situ gate oxide by O2 plasma-oxidized GaAs cap

Gucmann

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

et al. 2015

III-As heterostructure field-effect transistors (HFETs) and metal–oxide–semiconductor HFETs with gate electrodes insulated by an amorphous layer of ex-situ-prepared mixture of Ga and As oxides are studied. Gate insulator was prepared by O2 plasma oxidation of undoped GaAs cap layer of epitaxially grown transistor structures in standard plasma unit commonly used for photoresist ashing. GaAs cap is gradually consumed by the oxidation turning it into Ga and As oxides and causing bottom surface of the oxide moving closer to the two-dimensional electron gas. Gate electrode “recessing” is a positive byproduct of the process. Expectedly, impact on HFETs' threshold voltage (Vth) was observed and shift from −2.17 to −1.15 V was achieved. X-ray reflectivity confirmed much higher oxidation tendency for N-type GaAs than for undoped GaAs with this oxidation technique. Strong Vth shift can be most likely attributed to negative oxide charge in plasma-grown oxide or its interface with GaAs. Excluding Vth shift, negligible impact of O2 plasma on electrical characteristics was observed. Negligible Fermi level (EF) pinning inherited from the oxidation process can be concluded. Such O2 plasma-grown oxides might serve as an efficient seeding layer for subsequent high-κ gate dielectric growth. The authors believe this method might help to create a high-quality interface reducing number of Fermi level-pinning traps induced by other ex-situ deposition techniques while providing fine control over Vth as well.