Browsing by Author "Chou, ST"

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Alterable temperature-dependent wavelength shifts in (InP)(2)/(GaP)(2) quantum wells
(1998-02-02)
Cheng, YC
;
Tai, K
;
Chou, ST
;
Huang, KF
;
Tu, SL
Alterable temperature-dependent emission wavelength shifts were observed from (InP)(2)/(GaP)(2) short-period superlattices (SPSs) quantum wells grown with different interruption periods. Photoluminescence spectra showed that the peak energy of the SPS samples is inversely proportional to the interruption time conducted between the two consecutive binary growth sequences in the SPS regions. It is believed that a lateral composition modulation occurred during the interruption period which resulted in periodic In-rich and Ga-rich regions in the SPS quantum wells along the growth plane. With the lateral compositional variation, temperature variation can induce a multiaxial strain effect which can either amplify or reduce the temperature-dependent wavelength shift of the SPS quantum wells with different interruption periods. (C) 1998 American Institute of Physics.
Anomalous phosphorus cracker temperature-dependent photoluminescence spectra of InGaP grown by solid source molecular beam epitaxy
(2000-08-01)
Cheng, YC
;
Tai, KC
;
Chou, ST
;
光電工程學系
;
Department of Photonics
InGaP grown by solid source molecular beam epitaxy showed lower effective band-gap energy with increasing phosphorus cracker temperature. Anomalous photoluminescence (PL) spectra also indicated that a weaker ordering effect was initiated when the cracker temperature was higher. Since the variation of cracker temperature mainly changed the P-2/P-4 ratio, we believe that the more chemically reactive P-2 incorporates more In into the epilayer. Therefore, InGaP grown under a more Pt-rich condition has a higher In content which results in the lower band-gap energy instead of having an ordering effect.
AuBe Ohmic contacts to p-type ZnTe
(1998-12-10)
Lan, WH
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Lin, WJ
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Cheng, YC
;
Tai, K
;
Tasi, CM
Ohmic contacts of AuBe to p-ZnTe show a minimum specific contact resistance of 3.0 x 10(-6) Ohm cm(2) for a p-doping level of 1.6 x 10(19) cm(-3) and at an annealing temperature of 200 degrees C. The beryllium is very effective at improving the electrical properties of p-type contacts to ZnTe.
High-performance 30-period quantum-dot infrared photodetector
(2005-05-01)
Chou, ST
;
Lin, SY
;
Hsiao, RS
;
Chi, JY
;
Wang, JS
In this article, quantum-dot infrared photodetectors (QDIPs) with 10- and 30-period InAs/GaAs quantum-dot structures are investigated. High responsivity of 2.37 A/W and detectivity of 2.48 X 10(10) cm Hz(1/2)/W for 30-period QDIPs under 10 K are observed at -2.7 and 1.2 V, respectively. Almost symmetric photocurrents and dark currents under positive and negative biases are observed for both devices, which indicate a minor influence of the wetting layer on the performance of QDIPs. Lower dark current and increased photocurrent for the 30-period QDIPs would predict a better performance for devices with over a 30-period QD structure. (c) 2005 American Vacuum Society.
Ordering reduction in In0.5Ga0.5P grown by solid source molecular beam epitaxy
(1998-02-15)
Cheng, YC
;
Tai, KC
;
Chou, ST
;
Huang, KF
;
Tu, SL
In0.5Ga0.5P grown on GaAs substrates with different tilting angles by solid source molecular beam epitaxy (SSMBE) is studied. The results showed that a weak ordering effect still exists in SSMBE grown epilayers with tilted substrates. However, the ordering effect can be drastically reduced by growing In0.5Ga0.5P on a 15 degrees tilted substrate with an InAlP/InGaP superlattices (SL) buffer layer. The In0.5Ga0.5P epilayer grown by this method showed a peak photoluminescence (PL) energy of similar to 1.91 eV at room temperature, which is similar to the reported value for a fully disordered sample. The intensity of the ordering effect is characterized by polarized PL spectroscopy, and the reduction in the ordering intensity is attributed to the elimination of initial surface strain by the SL buffer layer.
Reduction of spontaneous surface segregation in (InP)(2)/(GaP)(2) quantum wells grown on tilted substrates
(1999-01-01)
Cheng, YC
;
Tai, KC
;
Chou, ST
;
Huang, KF
;
Lin, WJ
We have studied the growth mechanism of (InP)(2)/(GaP)(2) short-period superlattices (SPS) and In(0.5)Gao(0.5)P quantum wells grown on tilted substrates using solid-source molecular beam epitaxy (SSMBE). Both the (InP)(2)/(GaP)(2) SPS and In0.5Ga0.5P quantum wells show blue shifts of photoluminescence (PL) wavelengths when the substrate's tilting angle is increased. The blue shift is more prominent in the SPS structure than in the In0.5Ga0.5P quantum wells. By comparing FL, polarized PL spectra and transmission electron micrographs, we confirm that the ordering effect exists in both the (InP)(2)/(GaP)(2) SPS and In0.5Ga0.5P quantum wells when the substrate tilt angle is small, and can be greatly reduced when the substrate lilt angle is increased. We believed that the height and density of steps on substrates with larger tilt angles repress the segregation of group III adatoms.
Temperature and annealing effects on photoluminescence spectra of (InAs)(1)/(GaP)(2) superlattices grown by solid-source molecular beam epitaxy
(2000-10-01)
Cheng, YC
;
Chi, S
;
Chou, ST
;
Huang, KF
;
電子物理學系
Anomalous variation of photoluminescence (PL) wavelengths with temperature was observed in (InAs)(1)/(GaP)(2) short-period-superlattice (SPS) quantum wells grown by solid-source molecular beam epitaxy with different phosphorus and arsenic cracker temperatures. We believed that the anomalous PL behavior could be attributed to the multi-axial strain effect existed at the abrupt InAs and GaP interfaces in the SPS structure. After rapid thermal anneal (RTA) treatment, the anomalous PL spectra in the low temperature region disappeared but the high temperature PL characteristics remained, which revealed the thermal stability of the (InAs)(1)/(GaP)(2) quantum well structures and its potential in replacing InGaAsP quaternary.