Xue-Lun Wang

Strong photoluminescence from AlP/GaP disordered superlattice grown by atmospheric pressure organometallic vapor phase epitaxy using tertiarybutylphosphine

AlP/GaP disordered superlattices (d‐SLs) are grown for the first time by atmospheric pressure organometallic vapor phase epitaxy using tertiarybutylphosphine as the phosphorous source. Strong photoluminescence (PL) is observed from the d‐SL, comparing with the ordered superlattice (o‐SL) and the bulk alloy (b‐AL). The PL intensity of the d‐SL is 158 times stronger than that of the o‐SL and 114 times than that of the b‐AL. The strong PL from the d‐SL is attributed to the localized states created by the artificial disordering.

OMVPE Growth of AIP/GaP Superlattices Using Tertiarybutylphosphine as a Phosphorus Source

Abstract AlGaP layers and AlP/GaP superlattices were grown by atmospheric pressure OMVPE at low temperature on GaP substrates using tertiarybutylphosphine (TBP) as a phosphorus source for safety and using (NH 4 ) 2 S x solution for surface stabilization. High crystalline quality AlGaP epi-layers with specular surfaces were obtained at relatively low growth temperatures ( 4 ) 2 S x surface treatment. The AlP/GaP superlattices were grown at 725°C with a V/III ratio of 20 by using the (NH 4 ) 2 S x treatment. The X-ray diffraction profile showed satellite reflection peaks up to as high as fifth order for the (AlP) 17 /(GaP) 17 superlattice.

Enhanced electroluminescence of AlP/GaP disordered superlattice

Electroluminescent diodes with active layers of Al0.5Ga0.5P bulk alloy (b‐AL), (AlP)5/(GaP)5 ordered superlattice (o‐SL), and (AlP)m/(GaP)n (m,n=3,6,9) disordered superlattice (d‐SL) are fabricated by organometallic vapor phase epitaxy using tertiarybutylphosphine. Stronger injection electroluminescence is observed from the d‐SL diode as compared with the b‐AL and the o‐SL diodes. The total light output of the d‐SL diode is about 4–5 times stronger than that of the b‐AL and the o‐SL diodes. The result indicates the remarkable luminescence capability of the d‐SL.

OMVPE growth and characterization of AlxGa1−xP(0≤x≤1) using tertiarybutylphosphine

AlxGa1−xP(0≤x≤1) epilayers are grown by OMVPE using TBP as a phosphorus source. GaP epilayers with a specular surface are obtained at growth temperatures higher than 740°C with a V/III ratio of 20. The conduction type of the grown layers is n-type, and the carrier concentrations of the GaP layers are as low as 7.4 × 1014cm−3. In the growth of AlxGa1−xP, the growth rate, the Al distribution coefficient, and the electrical properties of the AlxGa1−xP epilayers exhibit very different behavior compared with those of AlGaAs grown by OMVPE.

Structure and photoluminescence of AlP/GaP short‐period superlattices grown by organometallic vapor phase epitaxy

Short‐period superlattices of (AlP)m/(GaP)n (m, n=4–11.5) are grown by atmospheric pressure organometallic vapor phase epitaxy using tertiarybutylphosphine as a phosphorus source. Structural and optical properties of the grown superlattices are characterized by double‐crystal x‐ray diffraction and photoluminescence (PL) measurements, respectively. By comparing the measured and the calculated full width at half‐maximum of satellite peaks, we find that very high quality superlattices with atomically abrupt heterointerfaces are achieved. Strong emission of bound exciton is observed at low temperature. The exciton emission, however, disappears quickly as the temperature is increased, and only PL lines due to impurity recombination remain at high temperature (≳30 K). No evident phonon replica is observed in the PL spectra. From these results, a direct band‐gap structure seems to be realized as expected from the zone‐folding effect. However, the absence of band‐to‐band direct transition at high temperature sugg...

Organometallic vapor phase epitaxial growth of AlP/GaP monolayer superlattice using tertiarybutylphosphine

The growth interruption time in the organometallic vapor phase epitaxial growth of AlP/GaP layers using tertiarybutylphosphine is optimized for the realization of an AlP/GaP monolayer superlattice. In the growth interruption, there exists an optimum time (2 s) beyond which the full width at half‐maximum (FWHM) of the x‐ray diffraction satellite peaks of an (AlP)5/GaP)5 superlattice becomes broader. The monolayer (AlP)1/(GaP)1 superlattice is realized for the first time in a AlP/GaP system. An average heterointerface roughness of as small as 0.12 A is estimated from the FHWM of the (001) diffraction peak of the (AlP)1/(GaP)1 superlattice.

Si and Zn doping of GaP grown by OMVPE using tertiarybutylphosphine

Si- and Zn-doping properties of GaP layers grown by organometallic vapor phase epitaxy (OMVPE) using tertiarybutylphosphine (TBP) are investigated. An electron concentration as high as 2.0 × 1019 cm−3 is easily achieved with a SiH4TMGa flow rate ratio of 2.2 × 10−3 and is higher than the value obtained by using gas source molecular beam epitaxy. The Si-doping efficiency seems to be considerably enhanced by the use of TBP compared with the case using PH3. The hole concentration of Zn-doped layers grown with TBP is comparable to that of PH3-OMVPE grown GaP layers, but the Hall mobilities are higher than those of PH3-OMVPE grown layers.

Reduction of carbon contamination in triethylphosphorus OMVPE GaP layers by Pt/Al2O3 catalyst

Abstract The use of a Pt/Al 2 O 3 catalyst during GaP growth using triethylphosphorus (TEP) OMVPE is presented. GaP layers are grown by atmospheric pressure OMVPE using TEP as a group-V source. Epilayers with mirror-like surface morphology are obtained with V/III ratio = 17 at 700°C. GaP growth was also conducted with a Pt/Al 2 O 3 catalyst introduced into the growth reactor. We show that carrier concentration in GaP is decreased by about an order of magnitude through the use of the Pt/Al 2 O 3 catalyst.

Structural Characterization of AlP/GaP Disordered Superlattice by Dynamical Simulation of X-Ray Diffraction

Dynamical simulation of X-ray diffraction is used to characterize structural properties of (AlP)m /(GaP)n (m, n=h, k, l) disordered superlattices (d-SLs). Many small diffraction peaks appear around the main peak, and peak intensities become weaker as the deviation from the average thickness increases. The observed diffraction patterns can be interpreted if the repetition of random series in the superlattice is taken into account. It is found that the total number of monolayers (MLs) of the 6 constituent layers or the average number of MLs of a d-SL can be precisely determined from the smallest peak separation or the angular distance between the main peak and the 0th-order diffraction peak.

Photoluminescence process in AlP/GaP short period superlattices grown by organometallic vapor phase epitaxy using tertiarybutylphosphine

Abstract Photoluminescence (PL) processes in (AlP) m /(GaP) m ( m =1–8 monolayers (ML)) short period superlattices grown by atmospheric pressure organometallic vapor phase epitaxy (OMVPE) using tertiarybutylphosphine (TBP) are investigated. Strong emission of bound excitons without phonon replicas is observed at low temperature. This suggests that the luminescence processes are of a direct transition. The transition probability is found to be very small since there is no band edge emission at high temperature. For the AlP/GaP superlattices with monolayer numbers greater than 4, the structural dependence of PL properties such as peak position and intensity qualitatively agree with the theoretically predicted results. However, direct to indirect transitions which are theoretically predicted for smaller monolayer numbers are not observed.