Photoelectrochemical etching of uniform macropore array on full 5-inch silicon wafers

We analyze the two main factors causing non-uniformity of the etched macropore array first,and then a novel photoelectrochemical etching setup for large area silicon wafers is described.This etching setup refined typical etching setups by a water cooling system and a shower-head shaped electrolyte circulator.Experimental results showed that the uniform macropore array on full 5-inch n-type silicon wafers could be fabricated by this etching setup.The morphology of the macropore array can be controlled by adjusting the corresponding etching parameters.

Effect of Different Etching Time on Fabrication of an Optoelectronic Device Based on GaN/Psi

Gallium nitride(GaN)/porous silicon(PSi)film was prepared using a pulsed laser deposition method and 1064 nm Nd:YAG laser for optoelectronic applications and a series of Psi substrates were fabricated using a photoelectrochemical etching method assisted by laser at different etching times for 2.5–15 min at 2.5 min intervals.X-ray diffraction,room-temperature photoluminescence,atomic force microscopy and field emission scanning electron microscopy images,and electrical characteristics in the prepared GaN on the Psi film were investigated.The optimum Psi substrate was obtained under the following conditions:10 min,10 mA/cm^(2),and 24%hydrofluoric acid.The substrate exhibited two highly cubic crystalline structures at(200)and(400)orientations and yellow visible band photoluminescence,and homogeneous pores formed over the entire surface.The pores had steep oval shapes and were accompanied by small dark pores that appeared topographically and morphologically.The GaN/Psi film fabricated through PLD exhibited a high and hexagonal crystallographic texture in the(002)plane.Spectroscopic properties results revealed that the photoluminescence emission of the deposited nano-GaN films was in the ultraviolet band(374 nm)related to GaN material and in the near-infrared band(730 nm)related to the Psi substrate.The topographical and morphological results of the GaN films confirmed that the deposited film contained spherical grains with an average diameter of 51.8 nm and surface roughness of 4.8 nm.The GaN/Psi surface showed a cauliflower-like morphology,and the built-in voltage decreased from 3.4 to 2.7 eV after deposition.The fabricated GaN/Psi film exhibited good electrical characteristics.

Precise photoelectrochemical tuning of semiconductor microdisk lasers

Micro-and nanodisk lasers have emerged as promising optical sources and probes for on-chip and free-space applications.However,the randomness in disk diameter introduced by standard nanofabrication makes it challenging to obtain deterministic wavelengths.To address this,we developed a photoelectrochemical(PEC)etching-based technique that enables us to precisely tune the lasing wavelength with subnanometer accuracy.We examined the PEC mechanism and compound semiconductor etching rate in diluted sulfuric acid solution.Using this technique,we produced microlasers on a chip and isolated particles with distinct lasing wavelengths.These precisely tuned disk lasers were then used to tag cells in culture.Our results demonstrate that this scalable technique can be used to produce groups of lasers with precise emission wavelengths for various nanophotonic and biomedical applications.