Referring to Fig. 1.52, what would appear to be an appropriate value of VK for this device...

Referring to Fig. 1.52, what would appear to be an appropriate value of V_K for this device? How does it compare to the value of V_K for silicon and germanium?

FIG. 1.52 Hewlett-Packard subminiature high-efficiency red solid-state lamp: forward current versus forward voltage;