Engineering Sciences: Electronics: Optoelectronic response of inter-crystalline phase change materials
Abstract
All-optical memory has historically been difficult to implement but desired for optical signal processing and tunable delay lines for signal routing and communication. Information transmission and storage in all-optical means have large potential bandwidth, low crosstalk, and zero energy waste on the optoelectronic conversion process. Free carrier and photothermal effect based optical bistable switches have been demonstrated at femtojoule pulse energy in silicon. Those switching mechanism in conventional semiconductors require a constant power supply for maintaining the logic states, and thus infeasible for energy-efficient optical signal processing. Recently, photonic phase change materials (PCM), especially Germanium Atimunide telluride (GST), has received great attention. Stoichiometric Ge2Sb2Te5 can be switched between crystalline and amorphous states within a nanosecond. Its high optical contrast and retention are also favorable for nonvolatile multi-level optical memory, which provides unique learning capability to hybrid silicon photonics mimicking neuron behavior. However, its crystalline states are highly absorptive in telecommunication bandwidth. To further reduce the energy consumption and insertion loss of phase-change devices, exploration of new photonic PCM materials are desired. PI proposes to explore a new photonic PCM In2Se3 and explore its transient and permanent optoelectronic variations undergo optical, electrical, and thermal stimulations. The interesting mix of volatile and nonvolatile switching dynamics promises new operational paradigms in the device and circuits level. The new photonic PCM In2Se3 is capable of reversible phase changes between a low-resistance crystalline phase and a high-resistance crystalline. The inter-crystalline phase transition in In2Se3 is melting-free, low-entropy phase changes, which is in contrast with the GeTe-Sb2Te3 superlattice film adopted in interfacial phase-change memory. In2Se3 has been used in electronic format but has not yet been explored in the optical domain. Its transparency in infrared wavelength range and lower switching energy are attractive for reducing the switching energy of PCM integrated silicon photonic switch and enabling novel functions of pure nonvolatile photonic phase tuners. The proposed research will focus on studying the mechanisms of the inter-crystalline transition of Molecular Beam Epitaxially grown In2Se3 and propose possible routes to reduce the electronic contact resistance and reduce optical switching power. Combining the micro-Raman spectra, refractive index spectra, tunneling electron microscope, atomic force microscope, and density functional theory calculation, the atomic structures and optical property transition upon thermal and electric stimulations will be investigated in crystalline In2Se3 samples. Molecular beam epitaxy (MBE) is capable of growing wafer-scale chalcogenide semiconductor materials with a well-controlled crystalline structure and bandgap. We will also explore the phase transitions in thermal evaporation prepared crystalline In2Se3 with lower cost and better scalability on the integrated photonic platform. Integrated hybrid optoelectronic devices will be fabricated to probe the local optoelectronic response of PCMs. The results include the transient and lasting nonlinear optical phenomena in inter-crystalline PCMs, the correlation between their atomic structural transitions and the dynamics of optoelectronic responses, demonstration of a hybrid device structure with ultra-low nonvolatile electro-optic and all-optical switching power.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 09, 2020
- Source ID
- W911NF2010078
Entities
People
- Tingyi Gu
Organizations
- Army Contracting Command
- United States Army
- University of Delaware