Abstract
AlGaAs/GaAs/AlGaAs double-heterostructures having two-dimensional electron and hole channels at the respective interfaces are studied by measuring their photocurrent and photoluminescence characteristics. Under the weak photoexcitation, it is found that photo-generated electrons and holes are driven by a built-in electric field between the two channels and flow out mostly as a photocurrent to the respective electrodes, making the photoluminescence negligibly small. When the excitation reaches a certain level, some of photo-generated electrons and holes accumulate in each channel and weaken the built-in field, leading to an exponential increase in photoluminescence or the radiative recombination of electrons and holes. When the excitation gets strong, photo-generated carriers are lost mostly in the form of photoluminescence, resulting in the saturation of photocurrent. A theoretical model to explain these findings is presented. A possibility of using this type of study to clarify operating mechanisms of super-junction devices is suggested.
Highlights
Si-based insulated-gate bipolar transistors (IGBTs) and super-junction (SJ) transistors are two important power devices that are widely used at present and in near future
To clarify the potential of such SJ devices based on 2D carriers, we fabricated an AlGaAs/GaAs/AlGaAs double-hetero (DH) structure devices that had a pair of electron/hole channels, as shown in Fig. 1(a); we investigated their transport characteristics by operating them as n- and p-channel FETs and as novel p-n diodes
When an n-type electrode to the electron channel and a p-type electrode to the hole channel are short-circuited, electrons and holes generated by a weak excitation light are driven to the nearby n- and p-channel regions and flow through the channel to reach their respective electrode, from which most of them flow out to the outside circuit as an external photocurrent
Summary
Si-based insulated-gate bipolar transistors (IGBTs) and super-junction (SJ) transistors are two important power devices that are widely used at present and in near future. Under the zero bias and reverse bias conditions increases linearly with the power of incident light, indicating that most of the photo-generated electrons and holes are separated by the built-in electric field, making the photoluminescence vanishingly small. As the excitation gets intense, the field is weakened so much that the photocurrent gets saturated, while the photoluminescence increases almost in proportion to the power of incident light, suggesting that the carrier collection process changes significantly. To explain these behaviors, a simple model based on the rate equation, covering both the transport and recombination processes of photo-generated carriers is developed
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