Notes

p-n-p Transistor …

p-n-p Transistor is:
Here two segments of p-type semiconductor (termed as emitter and collector) are separated by a segment of n-type semiconductor (termed as base).
All the three segments of a transistor have different thickness and their doping levels are also different. In the schematic symbols used for representing p-n-p Transistor and n-p-n Transistor, the arrowhead shows the direction of conventional current in the transistor.