Study On Performance Of Heterojunction Bipolar Transistor Based On GaAs

In this ever-changing era,human life has been inseparable from smart wearable devices,and these devices will use heterojunction bipolar transistors as part of the device.GaAs as the second generation semiconductor material is widely used.In this paper,GaAs,In P and In GaAs were used to build the model of heterojunction bipolar transistor,and the simulation software Silvaco was used to simulate the single heterojunction structure,double heterojunction structure and inverted structure,and the effects of doping concentration,thickness and temperature on the performance of the transistor were studied.Firstly,the bipolar transistor with single heterojunction structure is simulated and analyzed.The simulation results show that:（1）The breakdown voltage of the device will not change with the change of the concentration.When the base-emitter bias voltage V_be is≈0.7V,the current gain will fluctuate slightly,but the influence is not great.When the V_be increases,the current J_C and J_Bwill gradually increase,which enhances the ability of the emitting region and the base region to flow into the current.The corresponding current component will also increase.（2）Increasing the thickness of the collector layer can change the potential distribution on both sides of the heterojunction,thus enhancing the current inflow capacity of the emitting region and making each current component increase correspondingly.When the thickness of collector is less than 50nm,the current gain increases gradually.When the thickness is greater than or equal to 50nm,the current gain changes very little and can be ignored.Each current component will affect the change of current gain.Collector current and base current increase gradually with the increase of thickness.（3）in the temperature range 260K to 400K,open voltage declines with temperature rise,can use the temperature effect to explain the width of band gap semiconductor material temperature rise is likely to affect the crystal lattice of the material expansion and strengthen the lattice vibration,thus will reduce material band gap width,but when the temperature drops,the band gap will be bigger.And the Single Heterojunction Bipolar Tansistor（SHBT）also has a good temperature stability.Secondly,the InP/In_0.53Ga_0.47As/InP double heterojunction bipolar transistor is simulated and analyzed.The opening voltage of this Double Heterojunction Bipolar Tansistor（referred to as DHBT）can reach about 0.4V,which has a relatively good opening voltage.When the concentration reaches 4×10¹⁹cm^-3,the current gain can reach an optimal state.The peak value of In_0.53Ga_0.47As/In P DHBT can reach aboutβ≈125dβ,and the concentration has no strong effect on F_t and F_max.However,the current gain of In_0.53Ga_0.47As/In P DHBT will decrease slowly with the increase of doping concentration and base thickness.The current gain decreases when the base region thickness is increased.Changing the thickness can improve the DHBT output characteristics and the base region current injection.And DHBT has a good temperature stability,but also has a good thermal stability.These theoretical data provide basis for the preparation of high efficiency In GaAs/In P DHBT in the future.Last but not least,Silvaco software was used to simulate the inverted structure.It is found that the double-heterojunction bipolar transistor with inverted structure has higher common emitter DC gain,higher current output efficiency and better characteristic frequency than the conventional DHBT.The current gain and characteristic frequency of inverted DHBT can be improved by changing the temperature and thickness conditions.But at the same time,the temperature of the device will also rise,which will affect the functional use of the device.The increase of doping concentration will make the rate of DC gain and temperature rise faster,affecting the functional use of the device.At the same time,with the increase of doping concentration,the rate of characteristic frequency increase will decrease.Moreover,the DC gain has a negative temperature coefficient,and the characteristic frequency changes from a uniformly distributed positive temperature coefficient to a negative temperature coefficient.The thermal stability of the inverted structure is better than that of the conventional structure by changing the doping concentration and thickness.