Silicon diodes usually have a voltage drop of .6-.8 volts across them before they will fully conduct. Germanium diodes are usually in the range .5-.6 volts I believe.
The voltages you're quoting seem strange - if you can give the setup you're using to measure this, and the part # of the diodes you're using, a better answer can be given.
As it stands, I have to ask if you're measuring correctly.
Potential barrier of silicon is 0.7, whereas potential barrier of germanium is 0.3
The silicon diode (unless its a Schottky diode) conducts at approximately 0.6 volts. The germanium diode, however, conducts at a much lower voltage, typically 0.2 volts. This means that the germanium diode is better at small signal rectification applications, such as AM radio detectors, allowing a smaller tuner tank circuit.
A germanium diode has a lower forward voltage drop compared to a silicon diode, typically around 0.3V for germanium and 0.7V for silicon. Germanium diodes also have a higher reverse current leakage compared to silicon diodes.
The entire 1N40xx series of power diodes are all silicon. The OA79 small signal diode is germanium.
The typical value of the barrier potential for a germanium diode is around 0.3 to 0.4 volts. This barrier potential is the voltage required to overcome the potential barrier at the junction of the diode and allow current flow in the forward direction.
A silicon diode has a voltage drop of approximately 0.7V, while a germanium diode has a voltage drop of approximately 0.3V. Though germanium diodes are better in the area of forward voltage drop, silicon diodes are cheaper to produce and have higher breakdown voltages and current capabilities.
Silicon diodes have a higher forward voltage drop (~0.7V) compared to germanium diodes (~0.3V). Silicon diodes have higher temperature stability and are more commonly used in modern electronic devices, while germanium diodes are more sensitive to temperature changes and are less commonly used.
the cut in vol for silicon diode is 0.7 where as germaium is around 0.3 because of their construction( the ratio of majority n minority carreirs)
There is no exact substitute for a germanium diode, except another germanium diode. However if the only concern is to get a lower forward voltage drop than that of a silicon diode (0.7V), then a schottky barrier diode may be a suitable replacement as its forward voltage drop (<0.1V) is even lower than that of a germanium diode (0.2V).
silicon diode is preferred more when compared with germanium diode because in silicon diode the operating voltage is 0.7v where as in germanium diode the operating voltage is 0.3v , germanium is temperature sensitive so it can be easily destroyed by increasing temperature hence silicon diode is preferred more
cut in voltage *** for silicon is 0.7volts and that for germanium is 0.3volts.According to Millman and Taub, "Pulse, Digital and Switching Waveforms", McGraw-Hill 1965, the cutin (or offset, break-point or threshold) voltage for a silicon diode is 0.6, and 0.2 for germanium.Breakdown voltage is another thing entirely. It is the reverse voltage at which the junction will break down.
Simple, Use the multi-meter , switch to the diode option then connect the positive wire to the positive of diode n negative to the negative ( +ve wire red, -ve wire black) if the there is a reading of =~0.7V then it is silicon. and if it is =~ 0.3V then it is germanium.