Study Of Organic Thin-film Field Effect Transistors And High Power Remote Junction Lasers

Much attention has been attracted by organic thin-film field-effect transistors (OTFTs) as on/off and storage devices in the past decade. Compared to inorganic thin-film transistors, OTFTs are characterized with many advantages, such as low weight, flexibility, diversity, easy fabricating, low cost and large area. Because of their low cost and low temperature in fabricating, as well as better flexibility compared to silicon thin-film transistors, OTFTs are considered to be useful in driving liquid crystal display, organic light-emitting diodes (OLEDs), smart cards, smart price and inventory tags, and large-area sensor arrays. Pentacene, as widely used material to fabricate stable organic thin-film transistors, has the characters of high mobility and excellent electrical characteristics, therefore, pentacene OTFTs has become the focus in the study of OTFTs. In the current work, pentacene thin films with a comparative better quality were deposited by vacuum growing and self-designed level physical vapor growing systems and the fabrication characteristics of the thin-films were investigated. Furthermore, OTFTs were fabricated with pentacene as active material and electrical characteristics and degradation of the device were studied. On the basis of the physical vapor growing principle of organic thin-films, we designed and assembled the level physical vapor growing system which was applied to grow pentacene thin-films with better quality. The thin-films growing with the only (00l) face developed was consisted of single-crystal, poly-crystal and amorphous-crystalline-mixed and amorphous thin-films. The amorphous thin-films deposited on p-Si, n-Si and SiNx in the vacuum thermal evaporation. The pentacene thin-films were analyzed with x-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) and the thin-films in different growth system and different temperature were compared. After comparing, we concluded that the level physical vapor deposited pentacene thin-films had the characteristics of better quality, easy growing and low cost, but difficult to fabricate devices;the quality of pentacene thin-films deposited in vacuum was comparatively worse because the materials were not purified, but the thin-films could directly deposited on the substrate and easy to fabricate devices. Top contact OTFTs were fabricated by adopting gelatinized polyimide as the gate dielectric with physical vapor grown pentacene thin films pasted on it as the active layer; bottom contact OTFTs were fabricated by adopting SiNx as the gate dielectric with pentacene thin films deposited on it in vacuum as the active layer. Furthermore, the characteristics of the devices were measured and that of the threshold voltage, on/off current ratio and field effect mobility were calculated. The results showed that amorphous pentacene thin-films transistors deposited in vacuum obtained ahigher hole field-effect mobility of about 2.8 cm2/Vs, a lower threshold voltage of about 7.5V and on/off current ratio of about 105, as comparing with other devices. The reason of this is that the hole transport in amorphous pentacene thin-films may have critical effects on their electrical properties. The degradation of OTFTs was also investigated. In order to prevent from the H₂O molecules'adsorbing, Teflon was plated on OTFTs, thus the degradation was decreased. Abstract 2 With the rapid development of opto-electronic technique semiconductor lasers are widely used in optical fiber communication, optical sensor, information memory, medical treatment, opto-computer and pumping solid lasers. Especially the high power semiconductor lasers is compelling used in optical fiber amplifier and pumping source of solid lasers. At present how to enhance the output power of the high power semiconductor and prolong lifetime is a hotspot. In the article, according to the reason that the enhance of nonradiative recombination centers in active can cause the aging of the high power AlGaAs/GaAs lasers, we designed and fabricated a new AlGaAs/GaAs high power QW RJ lasers with 808nm wavelength. The separation of p-n junction from the active region was realized by doping the lower optical wave-guide layer with p-type. Though the high field of p-n junction could captive the move flaw and move them of active layer to p-n junction, this made the nonradiativere combination centers decline. It showed the threshold decline output power increased and aging of device becoming that of p-n junction, so it can enhance the reliability and lifetime of the device. The characteristics ofdirect current and lifetime, and the reliability of the devices were studied. We designed and fabricated high-power single-quantum-well remote junction semiconductor lasers, made some devices whose p-type confinement layer thickness were 0.1μm and 0.3μm separately. Based on the technique of electric derivative testing, the study on direct current properties and lifetime properties of about hundreds bar oxide AlGaAs/GaAs high power SQW remote junction lasers with 808nm wavelet were carried out. The result of the research showed that the device had good DC properties. To the lasers with 900μm cavity length, 100μm stripe width and the reflectivity of fore-and-aft cavity respective being 5% and 95%, the highest output of 800mW under 1A driving current and CW operation was obtained, and the best result of slope efficiency was as high as 1W/A, and the relative differential quantum efficiency was nearly 40%. Compared with the conventional AlGaAs/GaAs high-power semiconductor lasers, the remote-junction (RJ) high-power semiconductor lasers showed that the threshold current (Ith) and the threshold voltage (Vth) were larger because p-n junction had been transferred to between p-Al0.5Ga0.5As and n-Al0.5Ga0.5As, both of them with a wider band-gap. The lower confinement layer of RJ semiconductor lasers was densely doped as p-type, which might influence electron injection efficiency and lead to the increase of threshold current of the devices. Moreover, from the figure of the energy band structure of the device, we could see that p-n junction was separated from the active region, which made the minority-carrier move into the active region through diffusion and made the majority-carrier easily flow out of the active region. Though the majority-carrier current contributes nothing to radiative recombination, it made the threshold current increase. But, from the results of 0.1μm and 0.3μm thick p-Al0.3Ga0.7As confinement layers devices, the threshold current of 0.3μm thick...