Degradation Of Photoluminescence Intensity Research Articles

Effects of Heat Treatment on Bonding Properties in InP-to-Si Direct Wafer Bonding

Effects of heat treatment on bonding properties, which include bonding strength, photoluminescence intensity, and electrical conduction through the interface, have been investigated in InP-to-Si direct wafer bonding for the first time. Bonding strength and electrical conduction were found to be improved by heat treatment. On the other hand, a degradation of photoluminescence intensity was observed with high-temperature treatment.

Electroluminescence and photoluminescence from microporous silicon p-n junctions

A novel immersion scanning technique for making microporous silicon has been successfully applied to blank and lithographically patterned Si substrates. The advantages of the method lie in its simplicity, speed of fabrication, and adaptability to large and odd-size substrates. The photoluminescence (PL) intensity of porous silicon shows a steady decrease between 200 and 2 K and this behavior is fully reversible. Thermal desorption spectroscopy on microporous Si shows a classic hydrogen desorption spectrum which coincides with a quenching of the PL intensity. Under constant excitation, a degradation of PL intensity occurs in oxygen and wet nitrogen but is only partially reversible in dry N2. Microporous Si p-n junctions exhibiting normal I–V characteristics have been successfully fabricated with standard Si very large scale integrated processes. Visible light emission under forward bias is detected which increases linearly in intensity with input current. This is the first observation of electroluminescence in the visible region from microporous Si p-n junctions.

Rapid Photoluminescence Intensity Degradation in Porous Silicon

ABSTRACTRapid photoluminescence intensity degradation are observed in porous silicon layers formed at different preparation conditions. The decay rate, ranging from 0.5 to tens of seconds, is found to be a function of illumination intensity, sample temperature and emission wavelength. We attributed the degradation effect to photochemical reactions on the surface.

Characterization of Microporous Silicon Fabricated by Immersion Scanning

ABSTRACTA novel immersion scanning technique for making microporous silicon has been successfully applied to blank and lithographically patterned Si substrates. The advantages of the method lie in its simplicity, speed and adaptability to large and odd-size substrates. The photoluminescence (PL) spectra of microporous Si show a continuous decrease in intensity between 200K and 2K, but are fully reversible. Thermal desorption spectroscopy on microporous Si shows a classic hydrogen desorption spectrum which coincides with a quenching of the PL intensity. Under constant excitation, a degradation of PL Intensity occurs in oxygen and wet nitrogen but is only partially reversible in dry N2. Microporous Si PN junctions exhibiting normal I-V characteristics have been successfully fabricated with standard Si VLSI processes. Visible light emission under forward bias is detected which increases linearly In Intensity with Input current. This is the first observation of electroluminescence in the visible region from microporous SI PN junctions.

Organometallic growth and characterization of GaxIn1−xP (x=0.51, 0.65, 0.69)

The growth and characterization of GaxIn1−xP (x=0.51, 0.65, 0.69) are described in this paper. The organometallic vapor-phase epitaxial (OMVPE) growth was carried out in an atomospheric pressure reactor using trimethylgallium (TMGa), trimethylindium (TMIn), and phosphine (PH3). GaAs and commercially available hydride vapor-phase epitaxial GaAs0.70P0.30 and GaAs0.61P0.39 were used as the substrates. The influence of growth temperature and V/III ratio on the properties of the OMVPE epilayers was studied. This resulted in the determination of an optimum growth temperature of 625 °C and an optimum V/III ratio range of 40–50. The results of the mismatch due to the different lattice constants of the GaxIn1−xP epilayer and the substrate were investigated. It was found that high-quality GaxIn1−xP epilayers can be obtained only when the mismatch ‖Δa/a0‖ is less than 1×10−3. Under the conditions mentioned above, epilayers were reproducibly obtained with featureless surface morphologies, and photoluminescence (PL) with high intensities and narrow half-widths (41–43 meV at 300 K). The dislocation etch pit densities ρ of Ga0.65In0.35P and Ga0.69In0.31P epilayers were 7.4–8.6×104 cm−2, grown lattice matched to GaAs1−yPy ( y=0.30, 0.39) substrates with ρ=6.4–7.5×105 cm−2. The degradation of PL intensity after annealing at temperatures between 400 and 600 °C in H2 or N2 indicates an increase in the surface recombination velocity for GaInP epilayers. Etching 30 Å from the surface was found to restore the original PL intensity.

Degradation of photoluminescence intensity caused by excitation-enhanced oxidation of GaAs surfaces

Rapid degradation of photoluminescence (PL) intensity under high excitation level (∼1 kW/cm2) was observed at fresh surfaces of GaAs crystals made by various growth methods. The Auger analyses showed quick oxide formation at the photoexcited GaAs surfaces. The degraded PL intensity was recovered by etchings only the oxide layers; thus, the cause of PL degradation was ascribed to the increase of nonradiative recombination at the oxide-GaAs interface. The oxidation process was proved to be athermal. In contrast to GaAs, Al0.3Ga0.7As and InP showed no or slow degradations, respectively, under the same excitation condition.