Browsing by Author "Tai, KC"

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0.66 mu m InGaP/InGaAlP single quantum well microdisk lasers
(1998-06-01)
Pan, JS
;
Cheng, PH
;
Lee, TD
;
Lai, YC
;
Tai, KC
Visible emitting microdisk lasers with single InGaP/InGaAlP quantum well were demonstrated for the first time. Large spontaneous emission factors beta of 0.12 and 0.08 were observed for 5 and 10 mu m diameter disks, respectively.
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.
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.
Reachability testing: An approach to testing concurrent software
(1995-12-01)
Hwang, GH
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Tai, KC
;
Huang, TL
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資訊工程學系
;
Department of Computer Science
Concurrent programs are more difficult to test than sequential programs because of nondeterministic behavior. An execution of a concurrent program non-deterministically exercises a sequence of synchronization events called a synchronization sequence (or SYN-sequence). Non-deterministic testing of a concurrent program P is to execute P with a given input many times in order to exercise distinct SYN-sequences. In this paper, we present a new testing approach called reachability testing. If every execution of P with input X terminates, reachability testing of P with input X derives and executes all possible SYN-sequences of P with input X. We show how to perform reachability testing of concurrent programs using read and write operations. Also, we present results of empirical studies comparing reachability and non-deterministic testing. Our results indicate that reachability testing has advantages over non-deterministic testing.
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.