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Purpose: As human papillomavirus (HPV) is primarily responsible for the development of cervical cancer, significant efforts have been devoted to develop novel strategies for detecting and identifying HPV DNA in urine. The analysis of target DNA sequences in urine offers a potential alternative to conventional methods as a non-invasive clinical screening and diagnostic assessment tool for the detection of HPV. However, the lack of efficient approaches to isolate and directly detect HPV DNA in urine has restricted its potential clinical use. In this study, we demonstrated a novel approach of using polyethylenimine-conjugated magnetic polypyrrole nanowires (PEI-mPpy NWs) for the extraction, identification, and PCR-free colorimetric detection of high-risk strains of HPV DNA sequences, particularly HPV-16 and HPV-18, in urine specimens of cervical cancer patients. Materials and Methods: We fabricated and characterized polyethylenimine-conjugated magnetic nanowires (PEI/mPpy NWs). PEI/mPpy NWs-based HPV DNA isolation and detection strategy appears to be a cost-effective and practical technology with greater sensitivity and accuracy than other urine-based methods. Results: The analytical and clinical performance of PEI-mPpy NWs was evaluated and compared with those of cervical swabs, demonstrating a superior type-specific concordance rate of 100% between urine and cervical swabs, even when using a small volume of urine (300 µL). Conclusion: We envision that PEI-mPpy NWs provide substantive evidence for clinical diagnosis and management of HPV-associated disease with their excellent performance in the recovery and detection of HPV DNA from minimal amounts of urine samples.

Recently, distributed collaborative development environment has been recognized an alternative environment for product development in which multidisciplinary participants are naturally involving. Reuse of Product design information has long been recognized as one of core requirements for efficient product development. This paper addresses an image-based retrieval system to support product design information reuse. In the system, product images obtained from multi-modal devices are utilized to reuse design information. The proposed system conducts the segmentation of a product image by using a labeling method and generates an attributed relational graph (ARG) that represents properties of segmented regions and their relationships. The generated ARG is extended by integrating corresponding part/assembly information. In this manner, the reuse of assembly design information using a product image has been realized. The main advantages of the presented system are following. First, the system is not dependent to specific design tools, because it utilizes multimedia images that can be obtained easily from peripheral devices. Second ratio-based features extracted from images enable image retrievals that contain various sizes of parts. Third, the system has shown outstanding search performance, because we applied various information of segmented part regions and their relationships between parts.

Structural and optical properties of InGaN/GaN triangular-shaped multiple quantum well (QW) structures were investigated under various conditions of growth parameters such as growth temperature, flow rate of Ga and/ or In composition, and well and barrier widths. The optical properties affected by the growth parameters were well correlated with an In band gap, which is determined by the potential depth and the In composition in the well region. The emission peak energy was almost independent of the barrier width due to the relaxation of the piezoelectric fields in the triangular-shaped QWs. Photoluminescence spectra of the InGaN/GaN multiple QW structures showed a parabolic curve centered at 2.66 eV. The optical property of the triangular-shaped multiple QWs was substantially improved due to formation of quantum dot-like In composition fluctuations.

We have studied structural and electrical properties of one dimensionally grown single crystalline gallium nitride (GaN) nanowires (NWs) for nanoscale devices using a metal-initiated metal-organic chemical vapor deposition (MOCVD). GaN nanowires were formed via the vapor-liquid-solid (VLS) mechanism with gold, iron, or nickel as growth initiators and were found to have triangular cross-sections with widths of 15 ∼ 200 nm and lengths of 5 ∼ 20 μm. TEM confirmed that the nanowires were single crystalline and were well oriented along the [210] or [110] direction on substrate depending on the metal initiators. For electrical transport properties of un-doped GaN nanowires, the back-gated field effect transistors (FET) were also fabricated by standard e-beam lithography. In our electrical measurement, the carrier concentration and mobility were 2 ∼ 4 × 10 18 cm -3 and 60 ∼ 70 cm2/V s, respectively.

Structural and optical properties of InGaN/GaN multiple triangular quantum well (QW) structures with different threading dislocation (TD) densities of 1.5×108 (sample A) and 4.5×108 cm-2 (sample B) have been studied. High resolution transmission electron microscopy and x-ray diffraction analysis showed more fluctuation of local In composition in the sample B, which was attributed to the stress field created by the dislocations as it provides a driving force for the migration of In atoms towards dislocations. Severe degradation of photoluminescence intensity of the sample B was also observed at < 50 K. The optical and structural properties of the InGaN/GaN triangular QW structures are overall substantially affected by the TD density.

Substantial improvement of electrical and optical properties of InGaN/GaN multiple quantum wells (MQWs) was obtained with a triangular band structure. Transmission electron microscopy (TEM) images from the–50 nm. The light-emitting diodes (LEDs) with the triangular QWs showed a lower operation voltage, a higher light output power, and higher intensities and narrower line widths of electroluminescence spectra than those with the rectangular QWs. Very bright and uniform light emission from the triangular MQW LEDs was also observed at a low injection current, but spatially non-uniform emission from the rectangular ones.

The effects of the indium flow rate on the properties of InGaN/GaN quantum wells have been investigated by using atomic force microscopy, photoluminescence (PL), transmission electron microscopy and high-resolution x-ray diffraction. The high-indium content InxGa1?x N/GaN (x > 0.3) quantum wells used in this study were grown on c-plane sapphire by using metal?organic chemical vapour deposition. The indium flow rate in the quantum well layers was varied while keeping other growth parameters fixed. With increasing indium flow rate, the indium solid composition in the well layers increases and the magnitudes of the indium spatial fluctuations increase. However, the defects increase and the quantum well structure degrades. As a result, the PL peak position was redshifted and the intensity was reduced. The transmission electron microscopy images show that the quantum-dot-like regions are clear for InxGa1?x N/GaN (x = 0.35). Temperature- and excitation-power-dependent photoluminescence spectra support the results of transmission electron microscopy measurements. In addition, the electroluminescence spectra of the light emitting diode shows that the dominant mechanism in InGaN/GaN quantum wells is a localized effect in the quantum-dot-like regions. The V-defects originate at threading dislocations and the inversion domain boundary due to higher misfit strain with increasing indium flow rate.

We investigated the doping characteristics of Mg doped, Mg-Si co-doped, and Mg-Zn co-doped GaN films grown by metalorganic chemical vapor deposition. We have grown p-GaN film with a resistivity of 1.26 Ωcm and a hole density of 4.3 × 1017 cm−3 by means of Mg-Si co-doping technique. The Mg-Si co-doping characteristic was also explained effectively by taking advantage of the concept of competitive adsorption between Mg and Si during the growth. For Mg-Zn co-doping, p-GaN showing a low electrical resistivity (0.7 Ωcm) and a high hole concentration (8.5 × 1017 cm−3) was successfully grown without the degradation of structural quality of the film. Besides, the measured specific contact resistance for Mg-Zn co-doped GaN film is 5.0 × 10−4 cm2, which is lower value by one order of magnitude than that for only Mg doped GaN film (1.9 × 10−3Ωcm2).

Chlorofluorinated polyimides were prepared from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), and 2,2′-dichloro-4,4′-diaminobiphenyl (DCB) for optical waveguide applications. The resulting optical polymers exhibited good thermal stability, controllable refractive index, and low optical loss in the optical communication wavelengths of 1.3 and 1.55 µm. The control of refractive indices of the polymers was achieved by copolymerization of 6FDA/PFMB and 6FDA/DCB. As the amount of DCB was increased, the refractive indices of polymer were increased. The effect of addition of chlorine on optical properties of polymers such as absorption loss in the near-IR region were also investigated. Rib-type optical waveguides were fabricated using these chlorofluorinated polyimides. These waveguides exhibited low loss of less than 0.4 dB/cm for both TE and TM polarizations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 107–112, 1999

We studied the effects of the growth rate of a GaN buffer layer grown on a GaN epilayer. It was found that this growth rate plays a key role in improving the quality of the GaN film on a sapphire substrate and an optimum growth rate exists that yields the best crystal quality. A GaN film grown on a buffer layer with the optimum growth rate of 18.3 nm/min has an electron Hall mobility of 539 cm2/V s and a dislocation density of approximately 2×108 cm−2. These improvements of GaN film qualities are illustrated by the promotion of the lateral growth mode.

The material qualities of GaN overlayers grown on (0001) sapphire substrates by metal-organic chemical vapour deposition were investigated as a function of nitridation time. The nitridation of sapphire surface notably affects on the properties of the GaN overlayers, such as surface morphology and structural, optical and electrical properties. The GaN overlayer with a short nitridation time of 30 s shows a good surface morphology, a relatively low background Hall carrier concentration and a high electron mobility, but the defect-related emission around 550 nm increased. Furthermore, for the GaN overlayer with nitridation for 180 s, even though it has a low (102) full width at half-maximum of the high-resolution x-ray diffraction rocking curve, other material properties were degraded owing to the long nitridation time. It was found that material properties have a trade-off relationship with the variation of nitridation time.

A tetragonally distorted GaAs layer was grown on a Si(100) substrate by metalorganic chemical vapor deposition. From both the splitting and the shift of band-edge exciton lines in photoluminescence, the GaAs epilayer is found to be under biaxial tensile stress, which is quantitatively investigated using optical measurements, namely, Raman and temperature-dependent photoluminescence spectroscopy. The biaxial tensile stresses deduced from the intrinsic excitonic lines vary with temperature. The origin of the stress variation with temperature is discussed in detail. From the photoluminescence intensity ratios between the heavy- and light-hole excitonic transitions, the actual temperature where the conduction to heavy-hole band transition begins to predominate is found to be above 70 K.

The dependence of the forward operating voltage of In1−xGaxN/GaN light-emitting diodes (LEDs) on Mg flow rate during the growth of the p-GaN layer has been investigated. The hole concentration in the p-GaN layer increases with Mg flow rate up to a critical value and gradually decreases for higher flow rates. We find that the forward threshold voltage of the LEDs mainly depends on the Mg concentration in the p-GaN layer and is rather independent of hole concentration. A current flow mechanism involving the impurity acceptor band, instead of the usual valence band, is proposed to elucidate this anomalous behaviour of the I–V characteristics.

Recombination dynamics in InGaN / GaN multiple quantum wells (MQWs) having different well / barrier potential profiles were studied. Time-resolved photoluminescence (TRPL) signals of the MQWs having regular potential profiles (rectangular MQW) and those having the compositionally-graded barriers (trapezoidal MQW) exhibited similar stretched exponential decay, which is a fingerprint for localized exciton emissions. The luminescence lifetimes (τPL) of them were as long as 4-10 ns between 8 and 300 K, indicating the reduced wavefunction overlap due to the internal polarization fields. According to the analysis based on the model three-level scheme, little difference was found in the nonradiative lifetimes in the free / extended states between the two MQWs. However, the increase of the combined transfer and radiative lifetime with the increase in temperature from 8 to 300 K in the trapezoidal MQW was suppressed by a factor of 1.5 compared to that in the rectangular one, reflecting the recovery of wavefunction overlap and effectively larger localization depth due to the reduced effective field. As a result, the quantum efficiency of the trapezoidal MQW was improved by 40% compared to that of the rectangular one at 300 K.

A fabrication-tolerant Δκ directional coupler switch was fabricated in z -cut LiNbO 3 substrate by the annealed proton exchange method. In order to improve fabrication tolerance of the device, the metal mask was used for selective proton exchange as a self-aligned electrode, and the desired overlap of electrode and waveguide mode was accomplished by annealing process. Performing successive annealing of the device, at each annealing step the width mode size of the waveguide, the switching voltage of the device, and the crosstalk of two output waveguides were measured. The voltage-length product of the device is 28 Vmm at the wavelength of 633 nm and the crosstalk is smaller than -20 dB.

Temperature-dependent Hall effect measurements on unintentionally doped n-type GaN epilayers show that, above room temperature, the Hall-mobility values of different samples vary parallel with each other with temperature. We demonstrate that this anomaly is mainly due to a conductive layer near the GaN/sapphire interface for thin samples with low carrier density. Through trapping electrons, threading edge dislocations (TEDs) debilitate the epilayer contribution in a two-layer mixed conduction model involving the epilayer and the near-interface layer. The trapping may, in part, explain low mobility and anomalous transport in pure GaN layers. Scattering by TEDs is important only at low temperatures.

As integration of circuits increases, required feature size becomes smaller and smaller. Defect control becomes tighter due to decrease in defect size that affects the images printed on the wafer and increase in possibility to be killer defect like 2-face bridge defect. Therefore, particle sources from all processes should be controlled extremely. Especially for dry etching process, Alumina ceramic has been widely used for plasma resistance material such as electrode covering plate and insulator. However, they can be etched under 'F' series plasma condition as well, even in small amounts. It has been reported that non-volatile by-products from etch ceramic can be particle sources to be killer defect. Therefore, selection of ceramic materials must be important for particle control in dry etch process. This paper pertains to testing etch resistance differences in Alumina (Al 2 O 3 ) and Yttria (Y 2 O 3 ) ceramic materials depending on various density and surface roughness. Ceramic surface microstructures change after plasma treatment was observed with scanning electron microscope (SEM) and ceramic erosion rate after plasma treatment was measured with surface profiler.

Assembly design decision making is to provide a solution of currently violating design by evaluating assembly design alternatives with the consideration of the assembly design decision (ADD) criteria and of the causal interactions with manufacturing-environmental factors. Even though existing assembly design support systems have a systematic mechanism for determining the decision-criterion weight, the system still has a limitation to capture the interactions between manufacturing-environmental factors and ADD criteria. Thus, we introduce in this paper, Bayesian belief networks (BBN) for the representation and reasoning of the manufacturing-environmental knowledge. BBN has a sound mathematical foundation and reasoning capability. It also has an efficient evidence propagation mechanism and a proven track record in industry-scale applications. However, it is less friendly and flexible, when used for knowledge acquisition. In this paper, we propose a methodology for the indirect knowledge acquisition, using fuzzy cognitive maps, and for the conversion of the representation into BBN.

Athermal AWG multiplexer/demultiplexer prepared for E/C-band WDM-PON application, by a novel and practical psudo-passive alignment packaging method, demonstrates

Single crystal 3C-SiC epitaxial films are grown on Si(111) surfaces using tetramethylsilane by rapid thermal chemical vapor deposition. Strong blue/green photoluminescence (PL) was observed at room temperature from the free films of SiC prepared by etching the Si substrate. The main PL peak energy varies from 2.1 to 2.4 eV with full widths at half-maximum between 450 and 500 meV, depending on the growth condition, excitation wavelength and excitation light intensity. A weak peak at 3.0 eV also appeared. The infrared (IR) spectra of free films of SiC exhibit modes associated with CH and OH groups. We also compared PL characteristics of free films of SiC with those from porous SiC produced by anodization of SiC/Si to determine the origin of the PL. Porous SiC shows a PL peak centered at 1.9 eV, different from those in SiC. From the analysis of the IR spectra and scanning electron microscopic images, we tentatively suggest that the origin of the PL from free films of SiC might be associated with an OH group adsorbed on defects or some localized states as is the case for an amorphous SixC1−x alloy.

A channel waveguide formed in LiNbO/sub 3/ was fabricated by using distilled water instead of acids for proton exchange and a self-aligned SiO/sub 2/ cap for diffusion. It was demonstrated that the water reaction is an important reaction to cause the index change in proton exchange. >

Channel waveguides fabricated in LiNbO/sub 2/ by proton diffusion with a self-aligned SiO/sub 2/-cladding structure are discussed. Proton diffusion in width and depth directions is amenable to process parameters, so that it provides a simple method for control of mode profiles. Using this method, symmetric depth mode profiles and an aspect ratio of 1.15 at lambda =0.6328 mu m have been achieved for efficient fiber-to-waveguide coupling. >

Temperature-dependent Hall-effects in MOCVD-grown Si-doped GaN epilayers were measured as afunction of temperature in the range 10-800 K The results were satisfactorily analyzed in terms of a two-band model including the 1' and impurity bands at lower temperatures than room. The f band electrons are dominant only high temperatures. The ionized impurity scattering is the most important in the F band except at very high temperatures. Keywords: Electron transport, impurity band, two-band model, scattering mechanisms, gaffium nitride L INTRODUCTIONGallium nitride(GaN) is now viewed as one of the most important materials for semiconductordevice applications in short-wavelength optical emitters/detectors and high-power/high-temperature electrical devices1. Highly doped n-type GaN epilayers, commonly achieved by Si incorporation, are important for the device applications. Despite the considerable work and significant progress24, theelectron behaviors are not understood in detail especially in highly doped samples.

Si delta-doping in the GaN layer has been successfully demonstrated by low-pressure metalorganic chemical vapor deposition at a growth temperature of 1040°C. Si delta-doping concentration increases and then decreases with an increase in delta-doping time. This indicates that delta-doping concentration is limited by the desorption process owing to much higher thermal decomposition efficiency of silane at high growth temperatures of GaN. In addition, it was observed that the use of a post-purge step in the ammonia ambient reduces Si delta-doping concentration. From capacitance-voltage measurement, a sharp carrier concentration profile with a full-width at half maximum of 4.1 nm has been achieved with a high peak concentration of 9.8 x 1018 cm-3

In general, the optical waveguide in LiNbO3 integrated optics is a diffused type. Titanium indiffusion (TI) and proton exchange (PE) are well-known fabrication methods of a diffused waveguide. On the contrary, a ridge waveguide was fabricated by etching a LiNbO3 substrate[l,2]. Etching of the LiNbO3 substrate for the ridge structure was performed by a dry etching process, i.e., reactive ion etching (RIE), reactive ion-beam etching (RIBE), etc. A wet etching of LiNbO3 by using solution etchants, i.e., concentrated and dilute HF, HF:HNO3, etc., was nearly impossible to fabricate an integrated optic device, because of its low etch rate (several nm per minute) at room temperature and nonuniform etching[3]. Recently, it was reported that a proton-exchanged LiNbO3 has an etch rate about 1000 times larger than that of bulk LiNbO3. It also has a uniform etched surface in the 1HF:2HNO3 solution[4,5]. The method, wet etching after PE, is simple and has a larger etch rate than RIE or RIBE method which has an etch rate of the order of a few tens of nm per minute. In this paper, we report a novel fabrication method of a proton exchanged ridge waveguide by the wet etching of proton-exchanged LiNbO3.

We report on proton-diffused channel waveguides on Y-cut LiNbO3 fabricated by using pure benzoic acid for proton exchange and a self-aligned Si02 cap for diffusion. They do not exhibit surface damage since the rate of initial proton exchange can be lowered due to the proton conserving property of a selfaligned Si02 cap. The electrooptic property of the waveguide is investigated by the cutoff modulation of a channel waveguide. The proton diffusion with a self-aligned Si02 cap is proved to render good Y-cut LiNbO3 channel waveguides.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

1) Background: The diagnosis and treatment of intoxication induced by methyl bromide depends on the patient's exposure history. In the present case, the patient showed various neurologic symptoms which were helpful to confirm the diagnosis and to determine the concentration of bromide ion in his body. The reduction rate of bromide ion concentration was another important clue to estimate the patient's health state in treatment. Case report: Some neurologic disorders were manifested in a 35-year-old man who had been engaged in a fumigation company for 12 years. Although he had been complaining of abnormal symptoms for 10 days, he had left his work only 3 days before being admitted to our hospital in serious state via the emer- gency department. Comprehensive clinical evaluations confirmed he was suffering from polyneuropathy, optic neuropathy and cerebellar signs. We diagnosed his condition as methyl bromide intoxication, and ruled out other possible diseases, after taking his occupational history and evaluating the elevation of bro- mide ion concentration in the sampled blood, urine and cerebrospinal fluid. With decreasing bromide ion concentration, his abnormal symptoms improved and he was discharged 22 days after admission without any neurologic sequela. Conclusion: This case report confirmed the usefulness of measuring the concentrations of bromide ion in the diagnosis of methyl bromide intoxication. We therefore suggest that the regular measuring of bro- mide ion concentration be included in the occupation specified health examination.

The Fifth International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004) was held in Gyeongju, Korea from 15–19 March 2004. Gyeongju, the ancient capital of the thousand-year Silla kingdom (57 B.C. to 935 A.D.) provided additional pleasure to the participants as an exceptional open-air museum with antique treasures scattered all around the city. During the last decade we have witnessed remarkable developments in wide-gap semiconductors and light emitting devices in the spectral range from the visible to deep UV. The purpose of the Symposium was to provide a forum for intensive discussion on the issues and main progress especially in optoelectronic devices, material growth and characterization, and quantum structures of wide bandgap semiconductors. A total of 243 papers including 220 contributed and 23 invited ones were presented and discussed by 487 participants from 17 countries world-wide. Among them, 154 manuscripts were submitted and reviewed by the usual evaluation process of physica status solidi. Some were rejected or withdrawn, and finally 139 papers are published in the special issues of physica status solidi (a), (b), and (c). We gratefully acknowledge the referees for their careful review. The papers are grouped into 7 categories. The subheadings and the number of papers in each are as follows: Optoelectronic devices, 43; Growth and characterization, 45; Nano and quantum structures, 21; Contacts, 8; Zinc oxide, 9; Indium nitride and indium rich InGaN, 6; Others, 7. The special session of the Symposium, “The LED Highlight”, designed partially to meet the challenging targets of the technology, i.e., energy savings and clean environment preservation, drew much attention and is edited as a special coloured section in this issue. The next symposium is scheduled for Montpellier, France, in 2006. We wish the organizers of that symposium the best of luck and hope to see all of the ISBLLED-2004 participants again at ISBLLED-2006. ISBLLED-2004 was sponsored by The Research Society for the Wide-gap Semiconductors, Korean Physical Society, Office of Naval Research, Korea Science and Engineering Foundation, Korea Research Foundation, Korea Association for Photonics Industry Development, Asian Office of Aerospace Research and Development, and Korea Photonics Technology Institute. We would like to thank Ms. E. S. Hwang for her devotion to the preparation and the Proceedings of the symposium including the manuscript handling for publication.

The 5th International Symposium on Blue Laser and Light Emitting Diodes (ISBLLED-2004) was held in Gyeongju, Korea, 15–19 March 2004. The purpose of the symposium was to provide a forum for scientists and engineers to discuss recent progress and future trends in the rapidly advancing wide band gap semiconductor science and technologies and their applications in blue laser and light emitting diodes.

We investigated the effects of the in situ thermal cleaning treatment of a (0001) sapphire substrate surface in hydrogen ambient on the structural, optical, and electrical properties of epitaxial GaN films grown by metalorganic chemical vapor deposition (MOCVD). Hall effect, X-ray diffraction (XRD), and photoluminescence measurements of GaN films grown at 1040°C clearly indicate that the film quality is strongly affected by the thermal cleaning treatment of the substrate surface. GaN films under the optimized thermal cleaning treatment at 1070°C for 10 min showed minimum full-widths at half maximum (FWHMs) of 273 arcsec and 728 arcsec for (002) and (102) XRD peaks, respectively. In addition, the FWHM of the band-edge emission peak was as narrow as 28.3 meV, and the intensity ratio between the band edge emission and the yellow band emission was as high as 100 at room temperature. It was also found that the roughness of sapphire surface was reduced after the thermal treatment.

We report on vertical-cavity surface-emitting lasers (VCSELs) fabricated using selective oxidation to form a current aperture and an oxide surface barrier to seal buried AlAs layers in distributed Bragg reflectors. The lateral selective oxidation of the AlAs layer is strongly influenced by its thickness and heterointerface structures. The oxidation rate decreases rapidly with decreasing AlAs thickness in the range of < 80 nm, and the presence of AlGaAs layers on both sides of the AlAs layer reduces the oxidation rate. In addition, an oxide surface barrier with a thickness of ∼1 µm is formed by a brief wet oxidation which blocks diffusing oxygen species during the second wet oxidation. The effectiveness of the seal is demonstrated by using the oxide barrier as a mask against wet oxidation in the fabrication of oxide-confined VCSELs. The 8×8 µm2 devices with three quantum wells exhibit a threshold current of 400 µA, and the 4×4 µm2 single-quantum devices possess a threshold current as low as 85 µA.

Unintentionally doped GaAs layers were grown on semi-insulating GaAs substrates by metal-organic chemical vapor deposition. Temperature-dependent electrical transport measurements were performed and the layer characteristics were derived by a two-layer analysis. The substrate begins to affect the layer transport properties at low temperatures, depending on the carrier density and the layer thickness. The p-type samples show two conductivity-type conversions at two different temperatures. One is a combined transport phenomenon of the layer and substrate, and the other occurs in the layer but is still influenced by the substrate. A two-band model involving light- and heavy-hole bands was adopted in analyzing the hole transport in the layer, and the light hole was determined to play a crucial role even with its very small effective mass compared to the heavy hole.