Shih-Ying Yu

Characterization of low-resistance ohmic contacts to n- and p-type InGaAs

Multilayer ohmic contacts with differing first metal layers (M = Mo, Pd, Pt) beneath a Ti/Pt diffusion barrier and Au cap were fabricated on n+ and p+-InGaAs, and the relationship between their specific contact resistance and interfacial chemistry was examined. Palladium-based contacts offered the lowest specific contact resistances of ρc=3.2×10−8 and 1.9×10−8 Ω-cm2 to n+- and p+-InGaAs, respectively. The low resistances of the Pd-based contact were correlated with the formation of a uniform PdxInGaAs phase in direct contact with InGaAs, as observed using transmission electron microscopy and energy dispersive spectroscopy. On the other hand, the Mo-based contact to n+ and p+-InGaAs had much higher specific contact resistances, even though its specific contact resistance on lightly doped n-InGaAs was nearly the same as that of the Pd-based contact. The cause of this discrepancy was identified to be the native oxide layer that remained between the contact and semiconductor in the Mo-based contacts, as revea...

Sidewall passivation for InGaN/GaN nanopillar light emitting diodes

We studied the effect of sidewall passivation on InGaN/GaN multiquantum well-based nanopillar light emitting diode (LED) performance. In this research, the effects of varying etch rate, KOH treatment, and sulfur passivation were studied for reducing nanopillar sidewall damage and improving device efficiency. Nanopillars prepared under optimal etching conditions showed higher photoluminescence intensity compared with starting planar epilayers. Furthermore, nanopillar LEDs with and without sulfur passivation were compared through electrical and optical characterization. Suppressed leakage current under reverse bias and four times higher electroluminescence (EL) intensity were observed for passivated nanopillar LEDs compared with unpassivated nanopillar LEDs. The suppressed leakage current and EL intensity enhancement reflect the reduction of non-radiative recombination at the nanopillar sidewalls. In addition, the effect of sulfur passivation was found to be very stable, and further insight into its mechanism was gained through transmission electron microscopy.

Very low resistance alloyed Ni-based ohmic contacts to InP-capped and uncapped n+-In0.53 Ga0.47As

Successful application of the silicide-like NixInGaAs phase for self-aligned source/drain contacts requires the formation of low-resistance ohmic contacts between the phase and underlying InGaAs. We report Ni-based contacts to InP-capped and uncapped n+- In0.53Ga0.47As (ND = 3 × 1019 cm−3) with a specific contact resistance ( ρc) of 4.0 × 10−8 ± 7 × 10−9 Ω·cm2 and 4.6 × 10−8 ± 9 × 10−9 Ω·cm2, respectively, after annealing at 350 °C for 60 s. With an ammonium sulfide pre-metallization surface treatment, ρc is further reduced to 2.1 × 10−8 ± 2 × 10−9 Ω·cm2 and 1.8 × 10−8 ± 1 × 10−9 Ω·cm2 on epilayers with and without 10 nm InP caps, respectively. Transmission electron microscopy reveals that the ammonium sulfide surface treatment results in more complete elimination of the semiconductors native oxide at the contact interface, which is responsible for a reduced contact resistance both before and after annealing.

Single crystal small core semiconductor optical fibers for all-fiber optoelectronics

Recent development of fabricating small core single-crystal silicon and germanium optical fibers using a visible laser crystallization technique is reviewed. These fibers have potential applications in fiber-based nonlinear optical devices and optoelectronic applications.

Very low-resistance Mo-based Ohmic contacts to GeTe

Low-resistance and thermally stable Ohmic contacts are essential for radio frequency switches based on the unique phase change properties of GeTe. Herein, Mo-based Ohmic contacts to p-type GeTe are reported, including the effect of pre-metallization surface preparation and annealing on Mo/Ti/Pt/Au contacts. In-situ Ar+ plasma treatment resulted in a very low contact resistance of 0.004 ± 0.002 Ω mm (5 ± 3 × 10−9 Ω cm2), which could not be achieved using ex-situ surface treatments, highlighting the need for oxide-free interfaces to obtain very low contact resistance using Mo-based contacts. Experiments aimed at creating a more Ge- or Te-rich interface yielded higher contact resistances in both cases. The contact resistance increased for short-term annealing (30 min) above 200 °C and for long-term annealing (1 week) at 200 °C. No solid-state reaction between Mo and GeTe was observed using transmission electron microscopy with energy dispersive spectroscopy. However, Te migrated from GeTe after annealing at ...