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(a) EL image from a representative 50 μm-wide device stressed at Vgs = −15 V and Vds = 30 V for 760 s, where only the upper finger is biased. The EL image is overlaid on a white light image of the device. The numbers indicate the order of appearance of the EL spots. (b) EL integrated intensity as a function of stress time from each of the EL spots of (a) as indicated. The sum of the EL integrated intensities of all the seven spots is also shown. Curves are offset for clarity. The figure also shows Ig as a function of stress time. Vertical dotted lines are a guide to the eye.
(a) Electroluminescence image of a 100 μm-wide HEMT stressed at Vds = 40 V and Vgs = −15 V for 4 min. (b) and (c) AFM images of the areas inside the squares of (a) after removal of the passivation and contacts. The top and bottom dark bands in the images are the regions where the source and drain contact edges used to be before removal. The thickness and location of the gate contact before removal is indicated with arrows. The two light grey horizontal lines on both sides of the location of the gate contact in (b) are AFM artefacts.
(a) Topography image and (b) current image from two large surface pits. Both images were acquired simultaneously by using a conducting AFM tip at −10 V. Dotted lines indicate the location of the gate contact before removal. This device was stressed at both forward and reverse values of Vds , and thus shows surface pits on both sides of the gate.
(a) Standard-tip AFM image of one of the surface defects of Figure 2(b). (b) Depth profiles of the surface pit of (a) along the indicated arrows.
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