In Situ SiO₂ Passivation of Epitaxial (100) and (110)InGaAs by Exploiting TaSiO_x Atomic Layer Deposition Process

Abstract

In this work, an in situ SiO 2 passivation technique using atomic layer deposition (ALD) during the growth of gate dielectric TaSiO x on solid-source molecular beam epitaxy grown (100)In x Ga 1– x As and (110)In x Ga 1– x As on InP substrates is reported. X-ray reciprocal space mapping demonstrated quasi-lattice matched In x Ga 1– x As epitaxy on crystallographically oriented InP substrates. Cross-sectional transmission electron microscopy revealed sharp heterointerfaces between ALD TaSiO x and (100) and (110)In x Ga 1– x As epilayers, wherein the presence of a consistent growth of an ∼0.8 nm intentionally formed SiO 2 interfacial passivating layer (IPL) is also observed on each of (100) and (110)In x Ga 1– x As. X-ray photoelectron spectroscopy (XPS) revealed the incorporation of SiO 2 in the composite TaSiO x , and valence band offset (Δ E V ) values for TaSiO x relative to (100) and (110)In x Ga 1– x As orientations of 2.52 ± 0.05 and 2.65 ± 0.05 eV, respectively, were extracted. The conduction band offset (Δ E C ) was calculated to be 1.3 ± 0.1 eV for (100)In x Ga 1– x As and 1.43 ± 0.1 eV for (110)In x Ga 1– x As, using TaSiO x band gap values of 4.60 and 4.82 eV, respectively, determined from the fitted O 1s XPS loss spectra, and the literature-reported composition-dependent In x Ga 1– x As band gap. The in situ passivation of In x Ga 1– x As using SiO 2 IPL during ALD of TaSiO x and the relatively large Δ E V and Δ E C values reported in this work are expected to aid in the future development of thermodynamically stable high-κ gate dielectrics on In x Ga 1– x As with reduced gate leakage, particularly under low-power device operation.

Probing crystallographic orientation-specific carrier lifetimes in epitaxial Ge/AlAs and InGaAs/InP heterostructures

“…The structural analyses of these heterostructures can be found elsewhere. 5,16,33 A Probing facets in (110) InGaAs/InP heterostructures Atomic force microscopy analysis was performed from the surface of orientation-specific InGaAs/InP heterostructures. Fig.…”

“…Here, the temperature is referred to as the thermocouple temperature. The orientation-specific reduction of the growth temperature and group V/III ratios 16,33 were essential in order to reduce the surface faceting and surface adatom mobility during each heterostructure material synthesis. Each InGaAs/InP heterostructure was grown inside the group III-V reactor.…”

“…The details of these properties were reported in our earlier publications. 5,13,15,16,33 The surface morphology from the surface of each InGaAs/InP heterostructure was determined by atomic force microscopy (AFM). The carrier lifetimes were evaluated by the photoconductivity decay method 42 at the National Renewable Energy Laboratory, wherein the sample conductivity due to the excess carriers generated by laser excitation (wavelengths of 1500 nm and 1800 nm) was monitored via the microwave power reflected from each sample surface.…”

“…Here, the lattice matched epitaxial Ge and InGaAs layers were realized on GaAs substrate with an intermediate AlAs buffer layer and InP substrate, respectively. The respective substrate orientations were used for synthesizing orientation-specific Ge or InGaAs layers 16,33.…”

Atomic layer deposited tantalum silicate on crystallographically-oriented epitaxial germanium: interface chemistry and band alignment

“…This deposition process promoted the formation of an in situ interfacial SiO x layer at the TaSiO x /Ge interface. 50 Moreover, unlike the more thermodynamically stable and chemically robust native Si oxides, nonstoichiometric, easily-reduced native Ge oxides (i.e., GeO x ) have been known to correlate to a high density of (potentially charged) interface states. Furthermore, the water solubility of native Ge oxides, in addition to their low k value(s), frustrate the ability to effectively scale the equivalent oxide thickness (EOT) of composite dielectrics utilizing GeO x (either native or intentionally re-grown) as an interfacial passivating layer (IPL).…”