Procedure for Simulation

 

Combo Box and Sliders

 

• Select Material - This is used to select semiconductor material for doing the simulator.

 

•  Range of Current - One can choose the range of current for the current source.

 

•  Current’ Slider - It ranges from 1mA to 200mA. (Note:The divisions in the slider is fixed as 100). If 20mA current is selected in the combo      box, the slider value will range from 0mA to 20mA, with an interval of 0.2mA and if the value is 200mA in the combo box, slider value changes from 0mA to 200mA with an interval of 2mA.

 

• Range of oven - This combo box is used to fix the temeprature to a particular range.

 

•  Oven-  Oven is used to vary the temeprature upto 200⁰ C.

                Set Button – It is used to fix the temperature in the oven.

                Run Button – After setting the temperature, using run button we can start heating the oven.

                Wait Button – It is used to stop heating the oven at a particular temperature.

                Measure Button- It is used to display the present temperature of the oven.

 

• Select Range Combo Box – Options are X1 and X10.

 

• Temperature slider - it ranges from 27⁰ C to 200⁰ C. active only by clicking the Set button and become inactive after clicking Run button. If X1 is in combo box, the slider value ranges from 27 ⁰ C to 99⁰ C and If the value is X10 in combo box, slider value changes from 2.7 0 C to 200 C.

 

• Voltmeter Combo Box - Options are 1 mV, 10 mV, 100 mV, 1 V, 10 V.  One can select it for getting output in a particular range.

 

Procedure

1. Select the semiconductor material from the combo box.

2. Select the source current from the slider. Restrict the slider based on the range of current.

3. Select the Range of oven from the combo box.

4. Set the temperature from the slider.

5. Click on the Run Button to start heating the oven in a particular interval, from the default 25⁰C to the temperature that we set already Click on the Wait button to stop heating.

6. Click on the Set button to display the temperature that we set in the oven.

7. Click on the Measure button to display the present temperature in the oven.

8. Select the range of voltmeter from the combo box.

9. Measure the Voltage using Voltmeter.

10.Calculate the Resistivity of semiconductor in eV for the given temperature using equation (2) and (3).

11. A Graph is plotted with Temperature along x-axis and resistivity of semiconductor along y-axis.
 

 Procedure for Real Lab

 

In real lab, four probes are placed on the sample as shown in Fig:1.  Connections are made as  shown in the simulator. A constant current is passed through the outer probes by connecting it to the constant current source of the set up. The current is set to 8mA. The voltage developed across the middle two probes is measured using a digital milli-voltmeter. The trial is repeated by placing the four probe arrangement inside the oven. The oven is connected to the heater supply of the set up. For different temperatures, upto 150⁰C, the voltage developed is noted and tabulated.

The distance between the probes(S) and the thickness of the crystal (W) are measured. The values of (W/S) are calculated and the value of the function f(W/S) ia taken from the standard table. Using equation (2) and (3), calculate ρ for various temperatures.

 

Observations and Calculations

 

 Resistivity can be calculated by using the equation given below.

Here we take,

Distance between the probes, S as0.2cm and

Thickness of the sample,w as 0.05cm.

From standard table f(w/S) = 5.89

         =          ...................... Ohm cm

      =           ..................... Ohm cm

 

Result

 

 The resistivity of the given semiconductor by Four probe Method =  ...................................Ohm cm