الفهرس 
Introduction and Historical Review
Tunnel Diode DopingOnly 14 pages are availabe for public view
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Abstract
The present thesis is devoted in a trial to shed further light on some of
the most important electronic devices; tunnel diodes (TDs) - made of
(Gallium Arsenide; GaAs and Germanium; Ge) and back tunnel diodes
made of Ge- as well, silicon unijunction transistor (Si-UJT). These devices
are distinguished with negative differential resistance; (NDR) in their
electrical characteristics.
The electrical parameters of the different types of the proposed
devices and their applications were studied. As an example; oscillator
circuits based on TDs were investigated. For UJT, oscillator circuits; either
sinusoidal or relaxation were studied and presented. As well, solar engines
(BEAM-Type Robots) based on UJT either separate or combining with
Sillicon Controlled Rectifier; (SCR) i.e. hybrid system were implemented.
In this concern, various experimental work and different electronic
software packages [National Instruments Multisim (NI Multisim) and
Proteus] used for simulation were carried out. Moreover, applying
computer programs for calculating theoretical equations using MATLAB
language. Also, the work was extended to include the effect of different
environmental conditions [low and high temperatures, as well, electronand gamma- irradiation (based on cobalt-60 source)] on such devices and
their applications.
Detailed experimental-and simulation-studies of the initial electrical
characteristics for a wide spectrum of TDs were characterized. As an
example, samples of GaAs-TDs: (AИ301г, 3И301B, AИ301σ, Au301A),
samples of Ge-TDs (1N3712, 1N3716, 1N3718), and samples of Ge-back
TDs (BD1, BD4, BD7) were chosen and investigated. As well, the most
popular Si-UJTs (2N4870 and 2N2646) were utilized and their
characteristics were carried out.
I. Initial characteristics of the proposed devices:
A. For TDs:
- A set of electrical characteristic curves for TDs and back TDs were
plotted. The main electrical parameters of both diodes were deduced.They are: the peak-, valley-and forward-voltages (VP, VV, VF), as well,
the peak-and-valley-currents (IP, IV). Moreover, the other electrical
parameters; voltage-and current-spans, voltage swing, peak-to-valley
current ratio (IP/IV), output power (Pout) and finally, NDR were
calculated. Comparing both devices TDs and back TDs, it was clear that
the later had a suppressed Ip, hence, its characteristics approaches the
conventional diode characteristics.
B. For UJTs:
1. The emitter static characteristic curves (VE-IE) were plotted, for
(2N4870 and 2N2646) Si-UJTs, at different interbase voltage
(VB2B1) values. from which, the main electrical parameters (VP,
VV, IP, IV, NDR and intrinsic stand-off ratio; η) were deduced
and plotted for the two UJT types as a function of VB2B1.
2. The interbase characteristics (IB, VB2B1) were plotted at different
emitter current values. from which, it is proved that the obtained
relationships similar to the collector characteristics of a
conventional transistor.
3. The interbase resistance of UJT (RBB) was determined for the
two types, in case of open emitter. Its values were shown to be
around 7.27 k and 6.29 k, respectively.
II.The applications of the proposed devices:
A. For TDs:
Oscillator circuits were designed, implemented and tested based
on GaAs-TD for low frequency operating range and based on Geback TD for both the low-and high- frequencies.
For all the proposed systems, the output voltage waveforms were
plotted, from which, the main parameters of the proposed
oscillator circuit were deduced.
The frequency and VP-P of Ge-back TD oscillator dependence on
the bias voltage were investigated and plotted.B. For UJT:
- Sinewave oscillator circuit was designed, implemented and tested,
where the output voltage waveforms were plotted. from which,
the main parameters of the proposed sinewave oscillator were
deduced.
- The relaxation oscillator circuit was designed, implemented and
tested, where the output voltage waveforms were plotted, at
different operating and circuit element conditions. from which,
the main parameters of the proposed relaxation oscillator were
deduced.
- Two solar engine systems based UJT or UJT+SCR were designed,
implemented and tested, where the systems operation were proved
to be satisfactory. The designs of solar engines control circuits
based on either UJT or UJT+SCR were implemented, and their
output voltage, as well as, motor speed were tested under different
illumination levels. In this concern, for 6.0 Volts motors, 1200 and
1720 rpm were obtained for the two systems whenever the
polysilicon solar panel was illuminated up to around 50 klux.
III. Temperature effects
A.The characteristics of the proposed devices:
a. For TDs:
- For GaAs-TD and Ge-back TD, their electrical characteristics and
deduced parameters were plotted under the influence of a wide
temperature range (from -140 oC up to +101 oC, and from -81 oC up
to +70 oC, respectively).
1. For GaAs-TD, the electrical parameters (IV, VV, VF and Pout), rates
of changes due to temperature variations were shown to be; (+2.31
µA/oC, -0.44 mV/oC, -1.73 mV/oC and -0.54 µW/oC),
respectively. In addition, IP was shown to be independent of
temperature variations.
2. For Ge-back TD, the same parameters (IP, IV, VV, VF and Pout)
were shown to be; (-0.049 µA/oC, +0.046 µA/oC, -0.66 mV/oC,-1.34 mV/oC and -5.84 nW/oC), respectively.
Finally, for both diode types, VP was shown to be independent of
temperature variations.
3. Considering the performance metrics of GaAs-TD and Ge-back
TD, it was shown that for the first diode type, the rates of changes
of its parameters (voltage span, voltage swing, IP/IV and NDR),
due to temperature variations were shown to be;
(-0.44 mV/oC, -1.73 mV/oC, -67.13 and -6.062 kΩ/oC),
respectively. In addition, current span was shown to be
independent of temperature variations.
4. For Ge-back TD, the rates of change due to temperature
variations of the devices main parameters (current span, voltage
span, voltage swing, IP/IV and NDR), were shown to be; ( -0.095
µA/oC, -0.66 mV/oC, -1.34 mV/oC, -27.86, and +0.255 Ω/oC),
respectively.
b. For UJT:
- Concerning the operation of UJT within the temperature range
from -133 oC up to +125 oC, the (VE-IE) characteristic curves were
plotted.
1. The rates of changes of the main electrical parameters of UJT
(VP, VV, IP, IV, NDR, and RBB), due to temperature variations
were shown to be; (-2.91 mV/oC, -2.71 mV/oC, +4.99 nA/oC,
-13.49 µA/oC, +8.49 Ω/oC, -0.73 oC-1 and +33.99 Ω/oC),
respectively.
B. The applications of the proposed devices:
a. For TDs:
- The output voltage waveforms of the oscillator circuit were
plotted at different temperature levels, for GaAs-TD, within the
range from -173 oC up to +100 oC, and Ge-back TD, within the
range from -173 oC up to +65 oC. It is proved that both the
frequency and peak-to-peak voltage (VP-P) are temperature
independent.b. For UJT:
1. The output voltage waveforms of the sinewave oscillator circuit were
plotted at different temperature levels from -156 oC up to +65 oC. The
frequency was shown to be independent of temperature levels. On the
other hand, VP-P was affected with temperature which followed
Gaussian fitting, changes from around 4.0 Volts up to 4.72 Volts,
where its initial value was 4.88 Volts.
2. For the relaxation oscillator circuit based on UJT, its output voltage
waveforms were plotted at different temperature levels within the
range from -165 oC up to +125 oC. from which, the rates of changes
(dVP/dT and dVV/dT) due to temperature variations were shown to be;
-6.55 mV/oC and -5.17 mV/oC. In addition, the frequency was
increased from around 4.18 kHz up to 10.23 kHz. The charge time was
decreased from around 225 µsec down to 88 µsec, but the discharge
time was increased from 4.0 µsec up to 8.0 µsec.
IV. Radiation Effects
a. For TDs, (V-I) characteristic curves were plotted under the influence of
different electron irradiation dose levels:
For GaAs- and Ge-TDs: up to 3.73 MGy.
Both diode types were shown to be insensitive to low irradiation
levels, up to 1.0 MGy. For higher dose levels, the primarily failure
mechanism in both device types is an increase on (IP and IV), while
their (VV and VF) were shown to be decreased.
1. For GaAs-TD, the rates of changes of its electrical parameters (IP,
IV, VP, VV, VF and POut), due to electron irradiation effects were
shown to be; (+48.26 µA/MGy, +57.10 µA/MGy, -5.30 mV/MGy,
-80.99 mV/MGy, -65.68 mV/MGy and -7.53 mW/MGy),
respectively.
2. For Ge-TD, the rates of changes of the same parameters due to
electron irradiation effects were shown to be; (+45.58 µA/MGy,
+206.43 µA/MGy, +4.12 mV/MGy, -40.46 mV/MGy, -10.60
mV/MGy and -6.85 mW/MGy), respectively.3. Considering the performance metrics of GaAs- and Ge-TDs, it
was shown that all the parameters were decreased as a function of
the electron irradiation dose.
4. For GaAs-TD, the rates of change of its main electrical
parameters (current span, voltage span, voltage swing and
NDR), due to electron irradiation effects were shown to be;
(-6.23 µA/MGy, -75.69 mV/MGy, -60.38 mV/MGy and
-95.04 Ω/MGy), respectively. In addition, IP/IV was shown to
be decreased from around 17.75 down to 3.95.
5. For Ge-TD, the rates of changes of the same parameters, due to
electron irradiation effects were shown to be;
(-160.09 µA/MGy, -44.58 mV/MGy, -14.72 mV/MGy and
+11.92 Ω/MGy ), respectively.
Finally, IP/IV was shown to be decreased from around 7.89 down to
1.31.
b- For UJT, the dependence of (VE-IE) characteristic curves and
electrical parameters on gamma exposure dose: up to 10 MGy,
were plotted, where the following were recorded:
1. UJT parameters (VP, VV, IP, IV, NDR, and RBB) were shown
to be decrease pronouncedly as a function of the irradiation
dose, except its valley voltage, which, have an inverse trend,
i.e., increases.
2. For the determined parameters, the rates of changes due to
gamma irradiation effects were shown to be; (-195 mV/MGy,
+95 mV/MGy, -0.54 µA/MGy, -70 µA/MGy, -71 Ω/MGy,
-11.5 (MGy)-1 and -192 Ω/MGy), were deduced, respectively.