 working as an associate professor in electronics department at Wolchen Institute of Technology, Sholabor. In this video lecture we are going to discuss on a micro solid state device that is gun diode. Learning outcomes, after completion of this session students are able to describe construction working and characteristics of the gun diode. They are also able to know the application area. These are the contents which we will be discussing in this video lecture. Basically a gun diode is a semiconductor device which is formed by only n type of material like other type of semiconductor devices there is a p type and n type of and they form a junction that is why they are they form a diode. But it consists of a it consists of only n type of material but it consists of a 2 electrode. As this the devices has a lower energy level and higher energy layer. The electrons from the lower energy levels are being transferred into the higher energy level that is why these devices are called as a transverse electron devices. These devices are also or these diodes are also called as a negative resistance devices due to which they are used in a used to generate a microwave frequency at a low power or they may use as a low power oscillator to generate the microwave frequencies. Now, what is a negative resistance devices? Negative resistance devices allows the current in one direction at which its resistance is very low that is almost equal to 0 during it forward bias while even if it is consist of one type of material it gives the even it is forward bias it gives the 0 resistor. Similarly in a other direction it does not allow the current to flow as it offers a higher resistance during its reverse bias. This characters negative resistance characteristics is been observed in a devices. Now, let us see the internal structure and symbol of the gondaw. The symbol this is a symbol of the gondaw which is having the 2 electrode anode and cathode. If you see the internal structure of the gondaw it consists of a it is fabricated by the 3 layers in which the middle layer is likely doped compared with the other 2 layer. The middle layer is called as a active layer as this entire layer is fabricated or on a conducting material which acts as a heat sink and which also contribute as a electro cathode. If you observe here it there is a gold wire or gold alloy conducting material which is fabricated on the top surface which contribute the anode for the device. Working of the gondaw as we have previously said that it consists of only n type of semiconductor material in which electrons are a majority carriers. This electrons forms a current generate the current and this device utilizes the gun effect. Now, what is the gun effect? Let us discuss in a next slide. This diode is made of a single piece of n type of semiconductor material such as gallium arsenide or indium phosphate. As the gallium arsenide or indium phosphate are the have a high movability electron that is why they are used in constructing of the gondaw. The gallium arsenide has a one extra energy band bands in their electron band structure instead of having only 2 energy band that is a valence band and the conduction band. Now, what is a gun effect? It is a phenomena that occurs when the external voltage is applied to the gondaw. When the external voltage is applied the electrons from the lower energy band are passed into the higher electron higher energy band as it has a electrons has a mass the electrons moves from the lower energy band to the higher energy band when the external applied voltage exit the electrons from the higher energy band form a cluster of the electron. This form this cluster of electrons moves with the constant rate of the constant rate and this movements create a current in a device. This effect is called as a gun effect. Now, let us discuss the working with using this energy band diagram. In a gallium arsenide device it consists of is represented by 3 energy band that is valence band conduction band high energy band. Now, as the external applied voltage is increased the electrons from the valence band moves into the conduction band further increasing in the voltage external voltage the electrons from the conduction band moves into the higher energy band that is why they are called as a transverse electron devices. Now, once they moves into the higher energy band the mass increases as the mass increases this reduce in the mobility of this device decreases as the mass increases mobility decreases. Due to the mobility decrease and increase in the mass and as we further increase the voltage the electrons from the conduction band start moving coming back into the from the higher band start coming back into the conduction band due to this there is a decrease in the current. If you observe the VI characteristics of the gun diode initially this diode when there is a increase as the voltage increases the current also increases if we can see in this diagram the as the voltage is increasing current is also increasing linearly till the peak point the current increases after that peak voltage the current start decreasing and this will form a negative resistance in the device as the current start decreasing it decreases till the particular voltage which is called as a value point voltage after the value point voltage again the current start increasing in this way there are the current fluctuations in the devices that is why this creates the oscillations in the device that is why this devices can be used as an oscillator for generating the frequencies at a microwave range that is in a high frequency range. Now, let us see the applications where the gun diodes are being used as this gun diode previously discussed they are used as a gun oscillator to generate the frequency which are ranging from 5 gigahertz to 35 gigahertz and with the low power that is 100 milliwatt to 1 watt due to this they are used at a radio communication military and a commercial radio radar sources they are used for the remote vibrating detector and the rotational speed measuring tachometer the gun diodes are used as a pulse generating pulse gun diodes generating which are used for generating the micro current they are used in a micro transmitters to generate a radio waves at very low power they are also used as a fast controlling component in a micro electronics such as the modulations of the semiconductor injection laser and they are also used as a sub millimeters wave applications by multiplying the gun oscillator frequency with the diode frequencies these are the few applications areas due to which they are being used also they are used in a practical applications because as they are working with the low power in a academic these are the few references through which data is being collected