Growth of a 50 nm AlGaAs layer formed a heterojunction with this RT-GaAs channel. Figure 2(a,b) shows the layer structure and the calculated electric field distribution in devices with 1- and 3-��m electrode http://www.selleckchem.com/products/AP24534.html spacings under 9 V applied bias, respectively. Horizontal Inhibitors,Modulators,Libraries and selleck compound vertical axes have different scales. Nevertheless, the electric field vectors are primarily vertical, and are in the direction of growth. The electrostatic potential is shown on the right side in Figure 2(c,d), for the 1- and 3-��m spaced devices, respectively, using Synopsys Sentaurus TCAD device simulator, and modeling the LT-GaAs with trap density, type, and carrier mobility and lifetime values given in [4,5]; they also show the effect of vertical (y-direction) field lines in the LT-GaAs and RT-GaAs channel regions.
Figure 2.
Electric field distribution in devices with 1-��m (a) and 3-��m (b) electrode spacings under 9 V applied bias. The layer structure is also shown in the vertical axis, and has a different scale from horizontal axis. Vectors Inhibitors,Modulators,Libraries show the calculated …Four photodetector Inhibitors,Modulators,Libraries geometries were fabricated, which varied the separation between anode and cathode. The interdigital spacings were slightly asymmetric, producing average distances of 1.3, 3.2, 5.1 and 8.1 ��m, for the four Inhibitors,Modulators,Libraries devices. For the narrowest electrode gap (1.3 ��m), Inhibitors,Modulators,Libraries the average current�Cvoltage measurements are shown in Figure 3(a) at an average optical power of 11 ��W provided by a Ti:Sapphire source for the wavelength range of 770 to 920 nm.
The data in Figure 3(a) show a similar response for 770�C860 nm light with a peak current response at 800 nm.
At 890 nm and 920 Inhibitors,Modulators,Libraries nm, the wavelengths are near or below the band gap of GaAs so the photo-excited current decreases dramatically, although since we excite with short optical pulses their spectra even at 920 Inhibitors,Modulators,Libraries nm contain energy above the GaAs band edge. Using optical Inhibitors,Modulators,Libraries reflectance measurements (not shown), the GaAs and AlGaAs band edges are observed at 890 nm and 680 nm, respectively, as expected [11]. The samples exhibit a low dark currents of <0.5 nA at 10 V resulting in a high signal-to-noise ratio (>65 dB, as shown in Figure 3(a) even at the low excitation power of 11 ��W.Figure 3.(a) Current-voltage curves of the 1.
3 ��m device illuminated with 11 ��W average optical power at wavelengths ranging from 770�C920 nm, as well ambient room lights.
(b) Photocurrent profiles of a 1 ��m diameter, 200 �� …Spatial mapping of photocurrent within the electrode gap spacing Anacetrapib is performed GSK-3 by http://www.selleckchem.com/products/carfilzomib-pr-171.html useful site scanning a ~1 ��m diameter laser spot across a 7 ��m electrode spacing, for various bias voltages. Figure 3(b) shows that when a 200 ��W cw laser (780-nm wavelength) excites our sample, a peak current response is near the center of the gap for small applied bias (~2 V), and for large applied bias (+5 or �C5 V) the peak response is near the anode.