What is a common use for point contact diodes?

Point contact diodes are classically used as Radio Frequency (RF) detectors, such as in early crystal radios or microwave receivers. Their unique internal structure—a fine metallic wire resting delicately on a semiconductor crystal—results in extremely low internal capacitance. Because of this minimal capacitance, point contact diodes can easily rectify very high-frequency signals without their capacitive reactance shorting out the RF signal. This allows them to effectively extract the audio or data envelope from a high-frequency carrier wave. They are not suitable for high voltage rectification or acting as constant voltage sources because their delicate physical structure cannot handle significant power dissipation or high reverse voltages without burning out.