The light modulated Hall measurement system was set up in order to measure the minority carrier mobility of the p-type
HgCdTe material. Minority carrier mobility is one of the main parameters for HgCdTe infrared photodetectors, because
it determines the diffusion length of minority carriers, which plays a big role in the performance of optoelectronic
devices. Therefore, it is important to get the minority carrier mobility in HgCdTe, so as to evaluate the material property
before fabrication of photodetectors. By adding a modulated laser to the Hall system, the modulated Hall voltage was
measured on p-type Hg<sub>1-x</sub>Cd<sub>x</sub>Te(x=0.233) sample over a range of 0-1.8T in the magnetic field at temperature of 75K. The
modulated signal is generated by the movement of excess photocarriers in the magnetic field, so it has a relationship with
the magnetic field, the photogenerated carrier concentration and the electron and hole mobilities. Since the majority
concentration and mobility can be derived from the Hall effect, the minority mobility and the photogenerated carrier
concentration were obtained from fitting the light-modulated Hall voltage ▵V<sub>H</sub> as a function of the magnetic field B. As
compared to the references, the minority mobility we have obtained is reasonable, so the light-modulated Hall effect is
an effective way to obtain the minority carrier mobility.
HgCdTe infrared detector is designed to operate at cryogenic temperatures, so vacuum baking is a required process for
out-gassing in packaging of devices. As HgCdTe material, as well as ZnS passivation layer is sensitive to heat induced
changes, this process may be problematical for HgCdTe devices even at relatively low temperatures. We try to solve the
problems of heat instability by the fabrication of CdTe/ZnS double passivation layers. The effect of vacuum baking is
investigated through current-voltage (I-V) characteristics. We have compared the effects on devices with different
passivation layers. We have also compared the photodiodes fabricated on MBE grown HgCdTe on GaAs substrates and
LPE grown HgCdTe on CdZnTe. The devices were passivated with electron beam evaporated CdTe and ZnS and the p-n
junction was formed by ion-implantation. Through the analysis of I-V characteristics, we found that the devices
passivated with ZnS cannot afford vacuum baking even at 70°C, while the CdTe/ZnS- passivated devices can afford up
to 110°C temperature and the performance improved. After only 4 hours baking, the dynamic resistance of ZnS
passivation devices began to decrease and 10 hours later the zero-bias dynamic resistance (R0) decreased nearly 3 times.
Further baking of 110°C sees the maximum dynamic resistance of CdTe/ZnS passivation devices increase 2 to 4 times.
An insight into the mechanisms and parameters that are affected by vacuum baking is also gained by resistance-voltage
(R-V) curve fitting. The results also indicated the baking effects on LPE grown HgCdTe devices are almost same to
MBE grown HgCdTe devices.