We offer Dependence of Hall Coefficient on Temperature usefull in physics and material science lab. The Hall voltage for p-carriers has opposite sign from that for n-carriers. Therefore if a semiconductor with p-type doping is gradually heated up, more and more electrons from its valence band will go to conduction band. As a result hall voltage would fall rapidly with temperature and even become zero or change sign. At the point of zero Hall Coefficient, it is possible to determine the ratio of mobilities b=µe/µh. The Hall coefficient inversion is a characteristic of only p-type semiconductors.

The set-up consists of the following:
 
1. Hall Probe (Ge: p-type), HPP-22
Ge single crystal with four spring type pressure contacts is mounted on a glass-epoxy strip. Leads are provided for connections with the current source and Hall voltage measuring devices.
   
Oven
It is a small oven which could be easily mounted over the crystal or removed if required.

Temperature Sensor
Cromel-Alumel thermocouple with its junction at a distance of 1mm from the crystal.

2. Hall Effect Set-up :DHE-22
The set-up, DHE-22 consists of two sub set-ups, each consisting of further two units.

Measurement of Probe Current & Hall Voltage
This unit consists of digital millivoltmeter and constant current power supply. The Hall voltage and probe current can be read on the same digital panel meter through a selector switch.
   
(a) Digital Millivoltmeter
    Specifications
    Range: 0-200mV (100µV min.)
    Accuracy: ±0.1% of reading ±1 digit
    Impedance: 1MΩ
   
(b) Constant Current Power Supply
     Specifications
     Current: 0-20mA (10µA min)
     Accuracy: ±0.2% of the reading or ±1 digit
     Load regulated: 0.05% for 0 to full load
     Line regulation: 0.05% for 10% variation

Measurement of Thermo emf and Heater current
The unit consists of a digital millivoltmeter and constant current power supply. The thermo emf of thermocouple and heater current can be read on the same DPM through a selector switch.

(a) Digital Millivoltmeter
     Specifications :
     Range: 0-20mV
     Resolution: 10µV equivalent to 0.25°C in terms of thermo emf
    Accuracy: ±0.1% of reading ±1 digit

(b) Constant Current Power Supply
     Specifications
     Current: 0-1A
     Accuracy: ±0.2% of the reading ±1 digit
     Line regulation: 0.1% for 10% variation
     Load regulated: 0.1% for 0 to full load

5. Electromagnet, EMU-50V

6. Constant Current Power Supply, DPS-50

7. Digital Gaussmeter, DGM-202/ DGM-102

The experiment is complete in all respect.