Type Determination

Semilab developed a fast, non-contact method to determine conductivity type (P or N) of semiconductor material.  The basic theory behind the measurement relies on the SPV phenomenon.  Light hitting a semiconductor creates hole-electron pairs, and the carrier drift in the bulk of the material.  In p-type material, electrons enterring the depletion region will be accelerated to the surface, creating a negative surface potential.  In n-type material, it is the holes that will be accelerated to the surface, creating a positive surface potential.

Semilab’s type measurement technology uses a chopped light source to create an ac surface potential that is synchronously detected.  The polarity or phase of the signal tells the conductivity type.  In p-type material the detected signal is negative when the light is on, whereas in n-type material the signal is positive when the light is on.

Semilab’s PN-100 is a hand-held, battery operated type tester.  Type testing is also included in the RT-110, which measures resistivy, thickness and type at a single point of a wafer.