Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. The Institute for the Study of Labor (IZA) in Bonn is a local and virtual international research center and a place of communication between science, politics and business. IZA is an independent nonprofit organization supported by Deutsche Post Foundation. The center is associated with the University of Bonn and offers a stimulating research environment through its international network, workshops and conferences, data service, project support, research visits and doctoral program. IZA engages in (i) original and internationally competitive research in all fields of labor economics, (ii) development of policy concepts, and (iii) dissemination of research results and concepts to the interested public. Terms of use: Documents in D I S C U S S I O N P A P E R S E R I E SIZA Discussion Papers often represent preliminary work and are circulated to encourage discussion. Citation of such a paper should account for its provisional character. A revised version may be available directly from the author. Rank-order relative-performance evaluation, in which pay, promotion and symbolic awards depend on the rank of workers in the distribution of performance, is ubiquitous. Whenever firms use rank-order relative-performance evaluation, workers receive feedback about their rank. Using a real-effort experiment, we aim to discover whether workers respond to the specific rank that they achieve. In particular, we leverage random variation in the allocation of rank among subjects who exerted the same effort to obtain a causal estimate of the rank response function that describes how effort provision responds to the content of rank-order feedback. We find that the rank response function is U-shaped. Subjects exhibit 'first-place loving' and 'last-place loathing', that is subjects increase their effort the most after being ranked first or last. We discuss implications of our findings for the optimal design of firms' performance feedback policies, workplace organizational structures and incentives schemes.JEL Classification: C23, C91, J22, M12

Gate leakage/breakdown mechanism in unpassivated AlGaN∕GaN high electron mobility transistors (HEMTs) is investigated by performing temperature-dependent pulsed current–voltage (I–V) and current transient measurements of AlGaN∕GaN HEMTs without and with annealing after Schottky gate formation. After post-gate annealing, the devices exhibited significantly smaller gate leakage current and higher breakdown voltage even without any gate dielectrics or passivation layer. The temperature-dependent current transient measurements show that the current dispersion in the unannealed HEMTs is attributed to traps with an emission time constant (tE) of ∼0.5μs at 295 K and an activation energy of ∼38meV. On the contrary, the 20-min annealed devices have traps with tE of 21.6μs at 295 K and an activation energy of ∼0.31eV. The results suggest that the post-gate annealing removes shallow traps, and creates or activates deeper traps. We propose that the breakdown and gate leakage current is mainly due to the emission current from shallow traps in unpassivated AlGaN∕GaN HEMTs. The breakdown voltage improvement after the post-gate annealing is due to the removal of shallow traps near the Schottky gate metal∕AlGaN interface.

Influence of AlGaN barrier thickness on electrical and device properties in Al0.14Ga0.86N/GaN high electron mobility transistor structures J. Appl. Phys. 112, 053718 (2012) The inter-sublevel optical properties of a spherical quantum dot-quantum well with and without a donor impurity J. Appl. Phys. 112, 053717 (2012) Observation of a 0.5 conductance plateau in asymmetrically biased GaAs quantum point contact Appl. Phys. Lett. 101, 102401 (2012) Carrier control and transport modulation in GaSb/InAsSb core/shell nanowires Appl.

Ir, Ni, and Re Schottky contacts on strained Al0.25Ga0.75N/GaN heterostructures are characterized using capacitance–voltage (C–V) and I–V techniques. Based on the measured C–V characteristics, two dimensional electron gas sheet carrier concentrations at the AlGaN/GaN interface and barrier heights of Ir, Ni, and Re Schottky contacts are calculated. The barrier heights of 1.12, 1.27, and 1.68 eV are obtained for Ir, Ni, and Re Schottky contacts, respectively. The results show that the barrier heights of Schottky contacts on strained AlGaN/GaN heterostructures are strongly dependent on the metal work functions. However, contrary to Schottky contacts on bulk AlGaN or GaN, the barrier height on strained AlGaN/GaN heterostructures is lower for a Schottky contact with a higher metal work function. This is attributed to the stronger wave function coupling between electrons in the Schottky metal and surface donor electrons. The I–V characteristics for Ir, Ni, and Re Schottky contacts confirm the results obtained by C–V characteristics.

Room-temperature photoluminescence (PL) spectroscopy of II-VI semiconductor alloys has been proposed as a useful tool for determination of spatial variations in alloy concentration and impurity concentration. However, the nature of the PL recombination can affect the emission peak energy, as well as line shape. These effects in the band-edge emission of the compound II-VI semiconductor CdTe are reported here. PL measurements at 300 K were recorded from (1) highly doped n-type CdTe films grown by molecular-beam epitaxy, (2) undoped high-resistivity (p-10' -10 0cm) bulk CdTe, and (3) as-grown nominally p-type (p-10 -10' 0 cm) bulk CdTe. The dependence of PL emission intensity and line shape over a range of excitation from 0.003 -70 W/cm was studied. As the excitation power density was increased, a redshift in PL peak position was observed from all samples. PL peak position, intensity, and line-shape analysis show the highly excitonic nature of the radiative recombination in these materials, even though the free-exciton binding energy in CdTe is about 3 of kT at 300 K. In addition, the PL peak position can be more than 7 meV higher from n-type CdTe as compared to undoped CdTe.

Ground-penetrating radar (GPR) has been widely used to detect subsurface objects, such as hidden cavities, buried pipes, and manholes, owing to its noncontact sensing, rapid scanning, and deeply penetrating remote-sensing capabilities. Currently, GPR data interpretation depends heavily on the experience of well-trained experts because different types of underground objects often generate similar GPR reflection features. Moreover, reflection visualizations that were obtained from field GPR data for urban roads are often weak and noisy. This study proposes a novel instantaneous phase analysis technique to address these issues. The proposed technique aims to enhance the visibility of underground objects and provide objective criteria for GPR data interpretation so that the objects can be automatically classified without expert intervention. The feasibility of the proposed technique is validated both numerically and experimentally. The field test utilizes rarely available GPR data for urban roads in Seoul, South Korea and demonstrates that the technique allows for successful visualization and classification of three different types of underground objects.

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