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HL: Halbleiterphysik

HL 4: GaN: Bauelemente

HL 4.3: Vortrag

Montag, 24. März 2003, 11:00–11:15, BEY/154

Photoionization Spectroscopy on AlGaN/GaN HEMTs grown on sapphire and on silicon — •Mike Wolter¹, Peter Javorka¹, Michel Marso¹, Reinhard Carius², Hans Lüth¹, and Peter Kordoš¹ — ¹Institute of Thin Films and Interfaces - 1, Forschungszentrum Jülich, Germany — ²Institute of Photovoltaics, Forschungszentrum Jülich, Germany

The device performance of high electron mobility transistors (HEMTs) on AlGaN/GaN heterostructures is deteriorated by trapping processes. These processes are responsible for a reduction in the dc drain current (current collapse). The origin of the current collapse is assigned to deep level states in the layer system. Using photoionization spectroscopy we investigated these levels in HEMT structures grown by MOCVD on sapphire and on silicon. Whereas for HEMTs on sapphire we detected traps with excitation energies of about 3.2eV and 2.9eV, we found an additional trap at approximately 1.85eV for HEMTs on silicon. By varying the gate voltage we also found that a decrease of the gate bias leads to an increased photoionization cross section. This suggests that the concentration of electrons trapped in donor surface states has a strong influence on the current collapse process.