Try using a pull-up resistor (i.e. 1K) connected from the 6V power to the collector. I suspect, at 38khz, the signal at the collector would have a fast fall-time but have a very slow rise-time.
Try using a pull-up resistor (i.e. 1K) connected from the 6V power to the collector. I suspect, at 38khz, the signal at the collector would have a fast fall-time but have a very slow rise-time.