A. M. Sonnet

GaAs interfacial self-cleaning by atomic layer deposition

The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial “self-cleaning” is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements.

Detection of Ga suboxides and their impact on III-V passivation and Fermi-level pinning

The passivation of interface states remains an important problem for III-V based semiconductor devices. The role of the most stable bound native oxides GaOx (0.5≤x≤1.5) is of particular interest. Using monochromatic x-ray photoelectron spectroscopy in conjunction with controlled GaAs(100) and InGaAs(100) surfaces, a stable suboxide (Ga2O) bond is detected at the interface but does not appear to be detrimental to device characteristics. In contrast, the removal of the Ga 3+ oxidation state (Ga2O3) is shown to result in the reduction of frequency dispersion in capacitors and greatly improved performance in III-V based devices.

Frequency dispersion reduction and bond conversion on n-type GaAs by in situ surface oxide removal and passivation

The method of surface preparation on n-type GaAs, even with the presence of an amorphous-Si interfacial passivation layer, is shown to be a critical step in the removal of accumulation capacitance frequency dispersion. In situ deposition and analysis techniques were used to study different surface preparations, including NH4OH, Si-flux, and atomic hydrogen exposures, as well as Si passivation depositions prior to in situ atomic layer deposition of Al2O3. As–O bonding was removed and a bond conversion process with Si deposition is observed. The accumulation capacitance frequency dispersion was removed only when a Si interlayer and a specific surface clean were combined.

Comparison of n-type and p-type GaAs oxide growth and its effects on frequency dispersion characteristics

The electrical characteristics of n- and p-type gallium arsenide (GaAs) capacitors show a striking difference in the “accumulation” capacitance frequency dispersion. This difference has been attributed by some to a variation in the oxide growth, possibly due to photoelectrochemical properties of the two substrates. We show that the oxide growth on n- and p-type GaAs substrates is identical when exposed to identical environmental and chemical conditions while still maintaining the diverse electrical characteristics. The difference in electron and hole trap time constants is suggested as the source of the disparity of the frequency dispersion for n-type versus p-type GaAs devices.

Performance enhancement of n-channel inversion type InxGa1-xAs metal-oxide-semiconductor field effect transistor using ex situ deposited thin amorphous silicon layer

Significant enhancement in metal-oxide-semiconductor field effect transistor (MOSFET) transport characteristics is achieved with InxGa1−xAs (x=0.53, x=0.20) channel material using ex situ plasma enhanced chemical vapor deposited amorphous Si layer. InxGa1−xAs MOSFETs (L=2 μm, Vgs-Vt=2.0 V) with Si interlayer show a maximum drain current of 290 mA/mm (x=0.53) and 2 μA/mm (x=0.20), which are much higher compared to devices without a Si interlayer. However, charge pumping measurements show a lower average interface state density near the intrinsic Fermi level for devices without the silicon interlayer indicating that a reduction in the midgap interface state density is not responsible for the improved transport characteristics.

Impact of Semiconductor and Interface-State Capacitance on Metal/High-k/GaAs Capacitance–Voltage Characteristics

The frequency dispersion of the maximum capacitance of GaAs metal-oxide-semiconductor (MOS) capacitors is studied. The frequency dispersion behavior observed in the capacitance-voltage characteristics of GaAs MOS capacitors is a result of low semiconductor capacitance and an interface-state capacitance that varies with frequency. The traditional approach for calculating interface-state capacitance does not result in frequency dispersion of the maximum capacitance. An interface-state capacitance model based on an extremely high number of interface states in a thin disordered interfacial region is presented to explain the frequency dispersion behavior. The model shows an excellent match with the experimental results. The model also suggests that maximum capacitance values in low-frequency capacitance-voltage characteristics may be determined by the capacitance associated with the interface traps rather than the semiconductor charge and does not necessarily indicate the presence of free carriers.

Extraction of the Effective Mobility of In 0.53 Ga 0.47 As MOSFETs

The extraction of the effective mobility on In_0.53 Ga_0.47As metal-oxide-semiconductor field-effect transistors (MOSFETs) is studied and shown to be greater than 3600 cm²/V middots. The removal of <i>C</i> _it response in the split <i>C</i>-<i>V</i> measurement of these devices is crucial to the accurate analysis of these devices. Low-temperature split <i>C</i>-<i>V</i> can be used to freeze out the <i>D</i> _it response to the ac signal but maintain its effect on the free carrier density through the substrate potential. Simulations that match this low-temperature data can then be ldquowarmed uprdquo to room temperature and an accurate measure of <i>Q</i> _inv is achieved. These results confirm the fundamental performance advantages of In_0.53Ga_0.47As MOSFETs.

Extraction of the Effective Mobility of MOSFETs

The extraction of the effective mobility on In_0.53 Ga_0.47As metal-oxide-semiconductor field-effect transistors (MOSFETs) is studied and shown to be greater than 3600 cm²/V middots. The removal of <i>C</i> _it response in the split <i>C</i>-<i>V</i> measurement of these devices is crucial to the accurate analysis of these devices. Low-temperature split <i>C</i>-<i>V</i> can be used to freeze out the <i>D</i> _it response to the ac signal but maintain its effect on the free carrier density through the substrate potential. Simulations that match this low-temperature data can then be ldquowarmed uprdquo to room temperature and an accurate measure of <i>Q</i> _inv is achieved. These results confirm the fundamental performance advantages of In_0.53Ga_0.47As MOSFETs.

On the calculation of effective electric field in In0.53Ga0.47As surface channel metal-oxide-semiconductor field-effect-transistors

The effective electron mobility of In0.53Ga0.47As metal-oxide-semiconductor field-effect-transistors with HfO2 gate oxide was measured over a wide range of channel doping concentration. The back bias dependence of effective electron mobility was used to correctly calculate the vertical effective electric field. The effective electron mobility at moderate to high vertical effective electric field shows universal behavior independent of substrate impurity concentration.

Extraction of the Effective Mobility of

The extraction of the effective mobility on In_0.53 Ga_0.47As metal-oxide-semiconductor field-effect transistors (MOSFETs) is studied and shown to be greater than 3600 cm²/V middots. The removal of <i>C</i> _it response in the split <i>C</i>-<i>V</i> measurement of these devices is crucial to the accurate analysis of these devices. Low-temperature split <i>C</i>-<i>V</i> can be used to freeze out the <i>D</i> _it response to the ac signal but maintain its effect on the free carrier density through the substrate potential. Simulations that match this low-temperature data can then be ldquowarmed uprdquo to room temperature and an accurate measure of <i>Q</i> _inv is achieved. These results confirm the fundamental performance advantages of In_0.53Ga_0.47As MOSFETs.