arXiv subjects

Jörg Schulze

Publications and source records attributed to Jörg Schulze.

5 recordsLinked to original sources

arXiv2026

Impact of Surface Treatment on Noise in PL-Measurements of Silicon Vacancies in 4H-SiC Lateral pin-Diodes

Silicon vacancies ($V_\mathrm{Si}$) in 4H-SiC are promising candidates for quantum technologies due to their long spin coherence times and integrability into mature semiconductor platforms. However, conventional CMOS-compatible processing introduces significant photoluminescence noise from passivation layers and crystal damage, degrading color center coherence and excitation linewidths. This work evaluates strategies to minimize such background noise. Thermally grown oxides with nitrogen monoxide annealing provide excellent low-noise passivation, remaining stable during subsequent $600\,^{\circ}\mathrm{C}$ thermal treatments. Furthermore, combining reactive ion etching with atomic layer etching eliminates ion-induced surface damage. Into lateral pin-diodes, used for stark shift and photoluminescent excitation linewidth tuning, a selectively etched optical window is integrated. These devices show ideal electrical properties -- blocking up to $150\,\mathrm{V}$ with leakage current below $10\,\mathrm{pA}/μ\mathrm{m}$ -- while significantly enhancing the $V_\mathrm{Si}$ environment. Single emitters in these pin-diodes show an increased signal-to-noise ratio of 15 for near-surface and of 50 for deeper emitters on both c-plane and a-plane wafers.

quant-ph↗

arXiv2024

Lateral Mn5Ge3 spin-valve in contact with a high-mobility Ge two-dimensional hole gas

Ge two-dimensional hole gases in strained modulation-doped quantum-wells represent a promising material platform for future spintronic applications due to their excellent spin transport properties and the theoretical possibility of efficient spin manipulation. Due to the continuous development of epitaxial growth recipes extreme high hole mobilities and low effective masses can be achieved, promising an efficient spin transport. Furthermore, the Ge two-dimensional hole gas (2DHG) can be integrated in the well-established industrial complementary metal-oxide-semiconductor (CMOS) devices technology. However, efficient electrical spin injection into a Ge 2DHG - a prerequisite for the realization of spintronic devices - has not yet been demonstrated. In this work, we report the fabrication and low-temperature magnetoresistance measurements of a laterally structured Mn5Ge3/Ge 2DHG/ Mn5Ge3 device. The ferromagnetic Mn5Ge3 contacts are grown directly into the Ge quantum well by means of an interdiffusion process with a spacing of approximately 130 nm. We observe a magnetoresistance signal for temperatures below 13 K possibly arising from successful spin injection. The results represent a step forward toward the realization of CMOS compatible spintronic devices based on a 2DHG.

cond-mat.mes-hall↗

arXiv2019

Integrated collinear refractive index sensor with Ge PIN photodiodes

Refractive index sensing is a highly sensitive and label-free detection method for molecular binding events. Commercial implementations of biosensing concepts based on plasmon resonances typically require significant external instrumentation such as microscopes and spectrometers. Few concepts exist that are based on direct integration of plasmonic nanostructures with optoelectronic devices for on-chip integration. Here, we present a CMOS-compatible refractive index sensor consisting of a Ge heterostructure PIN diode in combination with a plasmonic nanohole array structured directly into the diode Al contact metallization. In our devices, the photocurrent can be used to detect surface refractive index changes under simple top illumination and without the aid of signal amplification circuitry. Our devices exhibit large sensitivities > 1000 nm per refractive index unit in bulk refractive index sensing and could serve as prototypes to leverage the cost-effectiveness of the CMOS platform for ultra-compact, low-cost biosensors.

physics.ins-det↗

arXiv2018

Optofluidic sensor system with Ge PIN photodetector for CMOS-compatible sensing

Vertical optofluidic biosensors based on refractive index sensing promise highest sensitivities at smallest area foot-print. Nevertheless, when it comes to large scale fabrication and application of such sensors, cheap and robust platforms for sample preparation and supply are needed - not to mention the expected ease of use in application. We present an optofluidic sensor system using a cyclic olefin copolymer microfluidic chip as carrier and feeding supply for a complementary metal-oxide-semiconductor-compatibly fabricated Ge PIN photodetector. Whereas typically only passive components of a sensor are located within the microfluidic channel, here the active device is directly exposed to the fluid, enabling top-illumination. The capability for detecting different refractive indices was verified by different fluids with subsequent recording of the optical responsivity. All components excel in their capability to be transferred to large scale fabrication and further integration of microfluidic and sensing systems. The photodetector itself is intended to serve as a platform for further sophisticated collinear sensing approaches.

physics.app-ph↗

arXiv2014

Hanle-effect measurements of spin injection from Mn5Ge3C0.8/Al2O3-contacts into degenerately doped Ge channels on Si

We report electrical spin injection and detection in degenerately doped n-type Ge channels using Mn5Ge3C0.8/Al2O3/n^{+}-Ge tunneling contacts for spin injection and detection. The whole structure is integrated on a Si wafer for complementary metal-oxide-semiconductor compatibility. From three-terminal Hanle-effect measurements, we observe a spin accumulation up to 10 K. The spin lifetime is extracted to be 38 ps at T = 4K using Lorentzian fitting, and the spin diffusion length is estimated to be 367 nm due to the high diffusion coefficient of the highly doped Ge channel.

cond-mat.mes-hall↗